Hello @Hazel - nice to hear from you again!
6. Can the Migration deport me after the registration of the marriage?
That depends on your girlfriend’s nationality/legal status. If she holds a German or EU passport then you have a right to stay with her (you will get a residence permit). You don’t need to have an asylum procedure at BAMF anymore in that case.
If she is a refugee with a residence permit then you can apply for family reunion after the wedding to live with her.
If your fiancé doesn’t fit the criteria listed above (for example if she is an asylum seeker) then you won’t be granted a residence permit through your marriage. In that case you still need to go through a regular asylum procedure.
1. How do I get the residence permit to stay after marriage? Do I have to apply for family reunification even when my asylum is still going or I don't have to wait for the decision from BAMF? How do I do it?
As I said above that depends on your fiancé’s nationality/legal status.
If the marriage with her entitles you to get a residence permit, you can apply for that at Ausländerbehörde.
2. If I don't give my passport what will happen? Will we still be allowed to marry or it will not be allowed?
You need to hand in your passport at Standesamt (registry office) in order to marry. I read that in some cases an expired passport might also work, but that might vary depending on the Standesamt you go to. I’d recommend to get in contact with them to find out what options you have.
3. How long does it usually take to get married?
You have to register your planned marriage at Standesamt. The earliest point in time when you can do this is 6 months before your wedding day. Keep in mind that it might take awhile to gather all the required documents.
4. Will I get my passport back after marriage?
Standesamt won’t keep your passport after marriage. They just need it to check your identity.
5. Will the Migration allow us to get married even though I’m an asylum seeker?
Yes, you are allowed to marry in Germany as an asylum seeker. Neither BAMF nor Ausländerbehörde are allowed to deny you this right.
I hope this answer was helpful to you!