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 'draeger-koeln'@'localhost' to database 'wildnisschule'.
Currently, the database is wildnisschule. The username is draeger-koeln and the database server is localhost.
For more help, see the Installation and upgrading handbook. If you are unsure what these terms mean you should probably contact your hosting provider.