We were able to connect to the MySQL database server (which means your username and password are okay) but not able to select the database.
The MySQL error was: Access denied for user 'server953169_kurzawa'@'%' to database 'server953169_kurzawa'.
Currently, the database is server953169_kurzawa. The username is server953169_kurzawa and the database server is mariadb1011.server953169.nazwa.pl.
For more help, see the Installation and upgrading handbook. If you are unsure what these terms mean you should probably contact your hosting provider.