Welcome to the Wefugees Community and thank you for reaching out to us.
As you can not leave the country in which your asylum case is pending, you may have to get married where you currently stay (which can be challenging as it usually requires a number of documents) and apply for a family reunification visa at the German embassy afterwards. Please not that I am not a lawyer and it is a quite difficult to give a tailored answer based on very little information. Maybe you contact a migration counselling centre for individal advice? If you want to share your approximate location, I could try to make some research on contact details/addresses.
All the best,