Dear @Hellothere,
Welcome back to the Wefugees Community.
I’m afraid that the registry office (Standesamt) will not accept an expired passport for the marriage. But the last decision will be at the discretion of the respective civil servant. I would recommend you to contact the registry office directly, explain your situation and see how they react. You may also check our blog about the marriage procedure and required documents.
Good luck and please don’t hesitate to keep us updated in this or to get back to us with any further questions.
All the best, Meike