So I did whitelist my IP now and its been working corectly. I can enable/disable mantenance mode via ssh although I still can’t do it by ticking the box “maintenance mode” while making backup but I;ve decided to go with it. Anyway. I’ve made both system and data + media backups.
At this point I’ve encountered another problem. I’ve triend to install a Unero theme for my website but something went wrong along the way (or at least so I presume). There was an error on both front and back end:
“An error has happened during application run. See exception log for details. Could not write error message to log. Please use developer mode to see the message.”
So I’ve set the mode to developer and front end shows this:
1 exception(s):
Exception #0 (Exception): Warning: Declaration of MGS\Mpanel\Block\Product\ImageBuilder::create() should be compatible with Magento\Catalog\Block\Product\ImageBuilder::create(?Magento\Catalog\Model\Product $product = NULL, ?string $imageId = NULL, ?array $attributes = NULL) in /var/www/html/app/code/MGS/Mpanel/Block/Product/ImageBuilder.php on line 0
Exception #0 (Exception): Warning: Declaration of MGS\Mpanel\Block\Product\ImageBuilder::create() should be compatible with Magento\Catalog\Block\Product\ImageBuilder::create(?Magento\Catalog\Model\Product $product = NULL, ?string $imageId = NULL, ?array $attributes = NULL) in /var/www/html/app/code/MGS/Mpanel/Block/Product/ImageBuilder.php on line 0
#0 /var/www/html/vendor/composer/ClassLoader.php(444): Magento\Framework\App\ErrorHandler->handler(2, 'Declaration of ...', '/var/www/html/a...', 0, Array)
#1 /var/www/html/vendor/composer/ClassLoader.php(444): include()
#2 /var/www/html/vendor/composer/ClassLoader.php(322): Composer\Autoload\includeFile('/var/www/html/v...')
#3 [internal function]: Composer\Autoload\ClassLoader->loadClass('MGS\\Mpanel\\Bloc...')
#4 [internal function]: spl_autoload_call('MGS\\Mpanel\\Bloc...')
#5 /var/www/html/vendor/magento/framework/ObjectManager/Relations/Runtime.php(38): class_exists('MGS\\Mpanel\\Bloc...')
#6 /var/www/html/vendor/magento/framework/Interception/Config/Config.php(166): Magento\Framework\ObjectManager\Relations\Runtime->has('MGS\\Mpanel\\Bloc...')
#7 /var/www/html/vendor/magento/framework/Interception/Config/Config.php(189): Magento\Framework\Interception\Config\Config->_inheritInterception('MGS\\Mpanel\\Bloc...')
#8 /var/www/html/vendor/magento/framework/Interception/ObjectManager/Config/Developer.php(61): Magento\Framework\Interception\Config\Config->hasPlugins('MGS\\Mpanel\\Bloc...')
#9 /var/www/html/vendor/magento/framework/ObjectManager/Factory/Dynamic/Developer.php(47): Magento\Framework\Interception\ObjectManager\Config\Developer->getInstanceType('MGS\\Mpanel\\Bloc...')
#10 /var/www/html/vendor/magento/framework/ObjectManager/ObjectManager.php(70): Magento\Framework\ObjectManager\Factory\Dynamic\Developer->create('MGS\\Mpanel\\Bloc...')
#11 /var/www/html/vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php(160): Magento\Framework\ObjectManager\ObjectManager->get('MGS\\Mpanel\\Bloc...')
#12 /var/www/html/vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php(246): Magento\Framework\ObjectManager\Factory\AbstractFactory->resolveArgument(Array, 'Magento\\Catalog...', NULL, 'productImageBui...', 'MGS\\AjaxCart\\Mo...')
#13 /var/www/html/vendor/magento/framework/ObjectManager/Factory/Dynamic/Developer.php(34): Magento\Framework\ObjectManager\Factory\AbstractFactory->resolveArgumentsInRuntime('MGS\\AjaxCart\\Mo...', Array, Array)
#14 /var/www/html/vendor/magento/framework/ObjectManager/Factory/Dynamic/Developer.php(59): Magento\Framework\ObjectManager\Factory\Dynamic\Developer->_resolveArguments('MGS\\AjaxCart\\Mo...', Array, Array)
#15 /var/www/html/vendor/magento/framework/ObjectManager/ObjectManager.php(70): Magento\Framework\ObjectManager\Factory\Dynamic\Developer->create('MGS\\AjaxCart\\Mo...')
#16 /var/www/html/vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php(160): Magento\Framework\ObjectManager\ObjectManager->get('MGS\\AjaxCart\\Mo...')
#17 /var/www/html/vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php(246): Magento\Framework\ObjectManager\Factory\AbstractFactory->resolveArgument(Array, 'MGS\\AjaxCart\\Mo...', NULL, 'processor', 'MGS\\AjaxCart\\Co...')
#18 /var/www/html/vendor/magento/framework/ObjectManager/Factory/Dynamic/Developer.php(34): Magento\Framework\ObjectManager\Factory\AbstractFactory->resolveArgumentsInRuntime('MGS\\AjaxCart\\Co...', Array, Array)
#19 /var/www/html/vendor/magento/framework/ObjectManager/Factory/Dynamic/Developer.php(59): Magento\Framework\ObjectManager\Factory\Dynamic\Developer->_resolveArguments('MGS\\AjaxCart\\Co...', Array, Array)
#20 /var/www/html/vendor/magento/framework/ObjectManager/ObjectManager.php(70): Magento\Framework\ObjectManager\Factory\Dynamic\Developer->create('MGS\\AjaxCart\\Co...')
#21 /var/www/html/vendor/magento/framework/Interception/PluginList/PluginList.php(250): Magento\Framework\ObjectManager\ObjectManager->get('MGS\\AjaxCart\\Co...')
#22 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(144): Magento\Framework\Interception\PluginList\PluginList->getPlugin('Magento\\Cms\\Con...', 'ajaxcart-action...')
#23 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(153): Magento\Cms\Controller\Index\Index\Interceptor->Magento\Framework\Interception\{closure}(Object(Magento\Framework\App\Request\Http))
#24 /var/www/html/generated/code/Magento/Cms/Controller/Index/Index/Interceptor.php(39): Magento\Cms\Controller\Index\Index\Interceptor->___callPlugins('dispatch', Array, Array)
#25 /var/www/html/vendor/magento/framework/App/FrontController.php(159): Magento\Cms\Controller\Index\Index\Interceptor->dispatch(Object(Magento\Framework\App\Request\Http))
#26 /var/www/html/vendor/magento/framework/App/FrontController.php(99): Magento\Framework\App\FrontController->processRequest(Object(Magento\Framework\App\Request\Http), Object(Magento\Cms\Controller\Index\Index\Interceptor))
#27 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Framework\App\FrontController->dispatch(Object(Magento\Framework\App\Request\Http))
#28 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(138): Magento\Framework\App\FrontController\Interceptor->___callParent('dispatch', Array)
#29 /var/www/html/vendor/magento/module-store/App/FrontController/Plugin/RequestPreprocessor.php(94): Magento\Framework\App\FrontController\Interceptor->Magento\Framework\Interception\{closure}(Object(Magento\Framework\App\Request\Http))
#30 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(135): Magento\Store\App\FrontController\Plugin\RequestPreprocessor->aroundDispatch(Object(Magento\Framework\App\FrontController\Interceptor), Object(Closure), Object(Magento\Framework\App\Request\Http))
#31 /var/www/html/vendor/magento/module-page-cache/Model/App/FrontController/BuiltinPlugin.php(69): Magento\Framework\App\FrontController\Interceptor->Magento\Framework\Interception\{closure}(Object(Magento\Framework\App\Request\Http))
#32 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(135): Magento\PageCache\Model\App\FrontController\BuiltinPlugin->aroundDispatch(Object(Magento\Framework\App\FrontController\Interceptor), Object(Closure), Object(Magento\Framework\App\Request\Http))
#33 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(153): Magento\Framework\App\FrontController\Interceptor->Magento\Framework\Interception\{closure}(Object(Magento\Framework\App\Request\Http))
#34 /var/www/html/generated/code/Magento/Framework/App/FrontController/Interceptor.php(26): Magento\Framework\App\FrontController\Interceptor->___callPlugins('dispatch', Array, NULL)
#35 /var/www/html/vendor/magento/framework/App/Http.php(135): Magento\Framework\App\FrontController\Interceptor->dispatch(Object(Magento\Framework\App\Request\Http))
#36 /var/www/html/generated/code/Magento/Framework/App/Http/Interceptor.php(24): Magento\Framework\App\Http->launch()
#37 /var/www/html/vendor/magento/framework/App/Bootstrap.php(258): Magento\Framework\App\Http\Interceptor->launch()
#38 /var/www/html/index.php(39): Magento\Framework\App\Bootstrap->run(Object(Magento\Framework\App\Http\Interceptor))
#39 {main}
Well, I guess answer is here but obviously I can’t find it. I’d really appreciate your help with this 
The back end just loaded, showed me log in tab and as I logged it it showed some terribly formatted code:
PDOException: SQLSTATE[HY000] [2002] No such file or directory in /var/www/html/vendor/magento/zendframework1/library/Zend/Db/Adapter/Pdo/Abstract.php:128 Stack trace:
#0 /var/www/html/vendor/magento/zendframework1/library/Zend/Db/Adapter/Pdo/Abstract.php(128): PDO->__construct('mysql:host=loca...', 'adminsp', 'J>scJ!__connect()
#2 /var/www/html/vendor/magento/framework/DB/Adapter/Pdo/Mysql.php(406): Zend_Db_Adapter_Pdo_Mysql->_connect() #3 /var/www/html/vendor/magento/zendframework1/library/Zend/Db/Adapter/Abstract.php(460): Magento\Framework\DB\Adapter\Pdo\Mysql->_connect()
#4 /var/www/html/vendor/magento/zendframework1/library/Zend/Db/Adapter/Pdo/Abstract.php(238): Zend_Db_Adapter_Abstract->query('SELECT `store_w...', Array)
5 /var/www/html/vendor/magento/framework/DB/Adapter/Pdo/Mysql.php(541): Zend_Db_Adapter_Pdo_Abstract->query('SELECT `store_w...', Array)
#6 /var/www/html/vendor/magento/framework/DB/Adapter/Pdo/Mysql.php(615): Magento\Framework\DB\Adapter\Pdo\Mysql->_query('SELECT `store_w...', Array)
#7 /var/www/html/vendor/magento/zendframework1/library/Zend/Db/Adapter/Abstract.php(737): Magento\Framework\DB\Adapter\Pdo\Mysql->query(Object(Magento\Framework\DB\Select), Array)
#8 /var/www/html/vendor/magento/module-store/App/Config/Source/RuntimeConfigSource.php(87): Zend_Db_Adapter_Abstract->fetchAll(Object(Magento\Framework\DB\Select))
#9 /var/www/html/vendor/magento/module-store/App/Config/Source/RuntimeConfigSource.php(57): Magento\Store\App\Config\Source\RuntimeConfigSource->getEntities('store_website', 'code')
#10 /var/www/html/vendor/magento/framework/App/Config/ConfigSourceAggregated.php(40): Magento\Store\App\Config\Source\RuntimeConfigSource->get('')
#11 /var/www/html/generated/code/Magento/Framework/App/Config/ConfigSourceAggregated/Proxy.php(95): Magento\Framework\App\Config\ConfigSourceAggregated->get('')
#12 /var/www/html/vendor/magento/module-store/App/Config/Type/Scopes.php(63): Magento\Framework\App\Config\ConfigSourceAggregated\Proxy->get()
#13 /var/www/html/vendor/magento/framework/App/Config.php(131): Magento\Store\App\Config\Type\Scopes->get('websites')
#14 /var/www/html/vendor/magento/module-store/Model/WebsiteRepository.php(183): Magento\Framework\App\Config->get('scopes', 'websites', Array)
#15 /var/www/html/vendor/magento/module-store/Model/WebsiteRepository.php(142): Magento\Store\Model\WebsiteRepository->initDefaultWebsite()
#16 /var/www/html/vendor/magento/module-store/Model/StoreResolver/Website.php(49): Magento\Store\Model\WebsiteRepository->getDefault()
#17 /var/www/html/vendor/magento/module-store/Model/StoresData.php(65): Magento\Store\Model\StoreResolver\Website->getAllowedStoreIds(NULL)
#18 /var/www/html/vendor/magento/module-store/Model/StoreResolver.php(138): Magento\Store\Model\StoresData->getStoresData('website', NULL)
#19 /var/www/html/vendor/magento/module-store/Model/StoreResolver.php(97): Magento\Store\Model\StoreResolver->getStoresData()
#20 /var/www/html/vendor/magento/module-store/Model/StoreManager.php(157): Magento\Store\Model\StoreResolver->getCurrentStoreId()
#21 /var/www/html/generated/code/Magento/Store/Model/StoreManagerInterface/Proxy.php(119): Magento\Store\Model\StoreManager->getStore(NULL)
#22 /var/www/html/vendor/magento/module-store/Model/Resolver/Store.php(30): Magento\Store\Model\StoreManagerInterface\Proxy->getStore(NULL)
#23 /var/www/html/vendor/magento/framework/App/Config/ScopeCodeResolver.php(49): Magento\Store\Model\Resolver\Store->getScope(NULL)
#24 /var/www/html/vendor/magento/framework/App/Config.php(69): Magento\Framework\App\Config\ScopeCodeResolver->resolve('stores', NULL)
#25 /var/www/html/vendor/magento/module-developer/Model/Logger/Handler/Debug.php(63): Magento\Framework\App\Config->getValue('dev/debug/debug...', 'stores')
#26 /var/www/html/vendor/monolog/monolog/src/Monolog/Handler/AbstractProcessingHandler.php(31): Magento\Developer\Model\Logger\Handler\Debug->isHandling(Array)
#27 /var/www/html/vendor/monolog/monolog/src/Monolog/Logger.php(344): Monolog\Handler\AbstractProcessingHandler->handle(Array) #28 /var/www/html/vendor/magento/framework/Logger/Monolog.php(48): Monolog\Logger->addRecord(400, 'SQLSTATE[HY000]...', Array)
#29 /var/www/html/vendor/monolog/monolog/src/Monolog/Logger.php(707): Magento\Framework\Logger\Monolog->addRecord(400, 'SQLSTATE[HY000]...', Array)
#30 /var/www/html/vendor/magento/framework/App/Bootstrap.php(263): Monolog\Logger->error('SQLSTATE[HY000]...')
#31 /var/www/html/index.php(39): Magento\Framework\App\Bootstrap->run(Object(Magento\Framework\App\Http\Interceptor))
#32 {main}
Next Zend_Db_Adapter_Exception: SQLSTATE[HY000] [2002] No such file or directory in /var/www/html/vendor/magento/zendframework1/library/Zend/Db/Adapter/Pdo/Abstract.php:144 Stack trace:
#0 /var/www/html/vendor/magento/zendframework1/library/Zend/Db/Adapter/Pdo/Mysql.php(111): Zend_Db_Adapter_Pdo_Abstract->_connect() #1 /var/www/html/vendor/magento/framework/DB/Adapter/Pdo/Mysql.php(406): Zend_Db_Adapter_Pdo_Mysql->_connect()
#2 /var/www/html/vendor/magento/zendframework1/library/Zend/Db/Adapter/Abstract.php(460): Magento\Framework\DB\Adapter\Pdo\Mysql->_connect()
#3 /var/www/html/vendor/magento/zendframework1/library/Zend/Db/Adapter/Pdo/Abstract.php(238): Zend_Db_Adapter_Abstract->query('SELECT `store_w...', Array)
#4 /var/www/html/vendor/magento/framework/DB/Adapter/Pdo/Mysql.php(541): Zend_Db_Adapter_Pdo_Abstract->query('SELECT `store_w...', Array)
#5 /var/www/html/vendor/magento/framework/DB/Adapter/Pdo/Mysql.php(615): Magento\Framework\DB\Adapter\Pdo\Mysql->_query('SELECT `store_w...', Array)
#6 /var/www/html/vendor/magento/zendframework1/library/Zend/Db/Adapter/Abstract.php(737): Magento\Framework\DB\Adapter\Pdo\Mysql->query(Object(Magento\Framework\DB\Select), Array)
#7 /var/www/html/vendor/magento/module-store/App/Config/Source/RuntimeConfigSource.php(87): Zend_Db_Adapter_Abstract->fetchAll(Object(Magento\Framework\DB\Select))
#8 /var/www/html/vendor/magento/module-store/App/Config/Source/RuntimeConfigSource.php(57): Magento\Store\App\Config\Source\RuntimeConfigSource->getEntities('store_website', 'code')
#9 /var/www/html/vendor/magento/framework/App/Config/ConfigSourceAggregated.php(40): Magento\Store\App\Config\Source\RuntimeConfigSource->get('')
#10 /var/www/html/generated/code/Magento/Framework/App/Config/ConfigSourceAggregated/Proxy.php(95): Magento\Framework\App\Config\ConfigSourceAggregated->get('')
#11 /var/www/html/vendor/magento/module-store/App/Config/Type/Scopes.php(63): Magento\Framework\App\Config\ConfigSourceAggregated\Proxy->get()
#12 /var/www/html/vendor/magento/framework/App/Config.php(131): Magento\Store\App\Config\Type\Scopes->get('websites')
#13 /var/www/html/vendor/magento/module-store/Model/WebsiteRepository.php(183): Magento\Framework\App\Config->get('scopes', 'websites', Array)
#14 /var/www/html/vendor/magento/module-store/Model/WebsiteRepository.php(142): Magento\Store\Model\WebsiteRepository->initDefaultWebsite()
#15 /var/www/html/vendor/magento/module-store/Model/StoreResolver/Website.php(49): Magento\Store\Model\WebsiteRepository->getDefault()
#16 /var/www/html/vendor/magento/module-store/Model/StoresData.php(65): Magento\Store\Model\StoreResolver\Website->getAllowedStoreIds(NULL)
#17 /var/www/html/vendor/magento/module-store/Model/StoreResolver.php(138): Magento\Store\Model\StoresData->getStoresData('website', NULL)
#18 /var/www/html/vendor/magento/module-store/Model/StoreResolver.php(97): Magento\Store\Model\StoreResolver->getStoresData()
#19 /var/www/html/vendor/magento/module-store/Model/StoreManager.php(157): Magento\Store\Model\StoreResolver->getCurrentStoreId()
#20 /var/www/html/generated/code/Magento/Store/Model/StoreManagerInterface/Proxy.php(119): Magento\Store\Model\StoreManager->getStore(NULL)
#21 /var/www/html/vendor/magento/module-store/Model/Resolver/Store.php(30): Magento\Store\Model\StoreManagerInterface\Proxy->getStore(NULL)
#22 /var/www/html/vendor/magento/framework/App/Config/ScopeCodeResolver.php(49): Magento\Store\Model\Resolver\Store->getScope(NULL)
#23 /var/www/html/vendor/magento/framework/App/Config.php(69): Magento\Framework\App\Config\ScopeCodeResolver->resolve('stores', NULL)
#24 /var/www/html/vendor/magento/module-developer/Model/Logger/Handler/Debug.php(63): Magento\Framework\App\Config->getValue('dev/debug/debug...', 'stores')
#25 /var/www/html/vendor/monolog/monolog/src/Monolog/Handler/AbstractProcessingHandler.php(31): Magento\Developer\Model\Logger\Handler\Debug->isHandling(Array)
#26 /var/www/html/vendor/monolog/monolog/src/Monolog/Logger.php(344): Monolog\Handler\AbstractProcessingHandler->handle(Array)
#27 /var/www/html/vendor/magento/framework/Logger/Monolog.php(48): Monolog\Logger->addRecord(400, 'SQLSTATE[HY000]...', Array)
#28 /var/www/html/vendor/monolog/monolog/src/Monolog/Logger.php(707): Magento\Framework\Logger\Monolog->addRecord(400, 'SQLSTATE[HY000]...', Array)
#29 /var/www/html/vendor/magento/framework/App/Bootstrap.php(263): Monolog\Logger->error('SQLSTATE[HY000]...')
#30 /var/www/html/index.php(39): Magento\Framework\App\Bootstrap->run(Object(Magento\Framework\App\Http\Interceptor))
#31 {main}