Getting marry

Germany has an entirely different system there is no prespouse visa.

But there are also very strict regulations against marrying relatives, so your intended spouse needs to research if you can legally marry here or if you marry elsewhere if Germany will accept it. Depends on the relation.

As far as the info you need, your future spouse needs to make an appointment with the registrar to get the info particular to your situation about what is required in your case and the appropriate steps. It is different for every country and often times even varies by city or just per person.

But do keep in mind it is a legal process including a court ruling so it will take a few months once all documents are submitted plus fees, so its not just quick and easy here.
Good luck