Schengen for fiancé

Good day everyone,

Just wanted to ask a question.

I am a German citizen living in South Africa.

I will be marrying a South African citizen in March next year, and we will proceed to go on honeymoon to Europe (but not through Germany at all) about 4 days after the ceremony.

My question - I know Germany sponsor Schengen visas for spouses/partners of German citizens, however, we will not have a marriage certificate by the time we’re going on the trip and I know it has to be done well in advance.

Do you think Germany will accept a document showing we live together, such as a medical scheme showing as spouse, as proof? Or a letter from our marriage authority stating the marriage will take place on the day it will next year?

Thanks for all the help! I am happy to answer any further questions anyone needs to ask for further information.