Hi Gregor Kastner,
your database cannot be supported anymore since you manually manipulated the tables.
The only feasible solution for you is to restore a backup of the database prior to the deletion of the tables. You can use DTW to transport the delta data since entered.
If the FA add-on is not working properly in that backup, you should contact your partner who will assist you. If your partner cannot solve the issue he logs a ticket with SAP.
All the best,
Kerstin