Hi @venz03chen
You send it to the BAMF office where you made your asylum application. In German called ‘BAMF Außenstelle’. I recommend you send it by registered post (‘per Einschreiben’) as an email is not sufficient for formal matters like these.
The only other option you have is to actually file an Untätigkeitsklage with the local administrative court (Verwaltungsgericht). I advise you to discuss both the threat to do so and actually filing such a case first with your lawyer. A lawyer should be taking such actions on your behalf.
Best,
Éanna