This is a pretty standard message that you’ll see if you need to update your version of phpMyAdmin. It can be ignored or you can follow the steps I’ve covered here: How to fix PARAMETER MUST BE AN ARRAY error in phpMyAdmin
The instructions that @PawelP mentions are pretty robust and should see you through.
The simplest way to reset your Owner/Permissions/Groups is to run the following command as a superuser from within the Magento root directory:
sudo find var generated vendor pub/static pub/media app/etc -type f -exec chmod g+w {} + && sudo find var generated vendor pub/static pub/media app/etc -type d -exec chmod g+ws {} + && sudo chown -R magento:www-data . && sudo chmod u+x bin/magento