Welcome to our community!
As Katrinsche already pointed out, you need to have a passport to marry.
You can try to get in contact with the Armenian embassy in order to get a passport. Some people say it's dangerous to go to the embassy because you might lose your legal status, but that's only true for people with a refugee status. In your case there is just an "Abschiebungsverbot". That means that you don't have a refugee status - so there is nothing to lose in the first place.
Source (German language): http://berlin-hilft.com/2017/04/25/passbeschaffung-wer-muss-wer-sollte-wer-darf-wer-nicht/
If both of you can provide a passport (and the other required documents) your boyfriend can come to Germany with a special visa that allows you to marry. After that you can apply for family reunion which will enable him to stay with you.
I highly recommend that he doesn't stay longer than the duration of his visa. Otherwise he resides here illegally which might cause trouble later on when he tries to re-enter Germany.