During installation I cannot proceed, cause the access to the MYSQL-Database is denied.

Message: Fehler!
PDO::MySQL berichtet: SQLSTATE[HY000] [1045] Access denied for user 'account100'@'localhost' (using password: YES)

With MySQLi it is the same: Fehler!
MySQLi berichtet: Access denied for user 'account100'@'localhost' (using password: YES)

What can I do?

Thanks in advance.

Either your database user or password is wrong(or both). Check the credentials in your zp-data/zenphoto.cfg.php file.

Or your database server is simply not localhost.

Thank you for your help. The reason was a $ sign in then password.