So, i got one step closer getting this issued solved.

Actually i expected the phpmyadmin or the built-in mlf recovery to create the required tables itself what it did not. And because the table prefix was different on the new database and the one backed up, i had this problem.

The import however fails when inserting the user data.
The table created on install seems to have more values than there are in my backup which is strange as i was running 2.4.6 and chose the exact same version for my plain installation.

As the backup file only contains the insert statements, it is hard to tell which values are missing in my sql dump. But from counting i can tell that there is a difference of only one value.