Welcome to our community!
This is a tricky situation.
I assume that you got a Duldung since you don't have any identification documents that are necessary to deport you, right? That means that you can't travel at the moment, but your fiancé can come over so that you two can get married here (it is possible to get married to a non-German in Germany having only a Duldung).
But there is a problem: In order to get married in Germany you need to provide valid documents that prove your identity (for example your ID). Handing them in at Standesamt could lead to your deportation if they tell the Ausländerbehörde about it.
But even if you get deported it’s still possible to marry your fiancé in another country. For example in your home country.