It looks like you have the correct timezone settings, so the issue may be related to the MariaDB server. Try setting the timezone for the MariaDB server to the same timezone as your application. You can do this by running the following command in the MariaDB console:
SET GLOBAL time_zone = 'Europe/Berlin';
If that doesn't work, you can also try setting the timezone for the connection when you create it. You can do this by adding the following line to your database config file:
'options' => [PDO::MYSQL_ATTR_INIT_COMMAND => "SET time_zone = 'Europe/Berlin'"]