This is really a long time you have been waiting for an answer from BAMF.
I can imagine how frustrating and blocking the effects of this lack of response must be for you.
The only additional advice i can give you, if you want to speed up the process, is to get into offensive to the BAMF. There is always the possibility to sue the BAMF because they did not send you any response until now.
I am not a lawyer. But in your case the time span that passed since your interview is unbearable. A court case would bring more pressure on the BAMF in this case, but of course bears the risk of additional costs for you!
It seems to be the outcome of such a lawsuit, that the BAMF is not
convicted but, that the court sends an official question to them when to expect a decision, which taken alone, often speeds up the process.
If you want to go the legal way you should contact the Flüchtlingsrat in
your federal country and ask them about their experience and for advice.
We already covered the topic here:
All the best