Welcome back to the Wefugees Community and thank you for reaching out to us.
Section 28 (2) of the German Immigration act says the following:
"(2) As a rule, the foreigner must be granted a permanent settlement permit if he has possessed a temporary residence permit for three years, the family unit with the German continues to exist in the federal territory, there is no public interest in expelling the foreigner and the foreigner has a sufficient command of the German language. Section 9 (2) sentences 2 to 5 shall apply accordingly. The temporary residence permit shall otherwise be extended as long as the family unit continues to exist."
You may also want to check this website which lists the prerequisites for the permanent residence permit for a spouse of a German citizen in detail (the website is published by Berlin authorities, similar regulations will apply to other regions in Germany as well though).
Unfortunately, you will need to hold the residence permit (incl. the time you hold a visa for the purpose of family reunification) for at least three years before you can apply for the permanent settlement. Please also keep in mind, that you might need to prove that you can cover your costs of living and are not dependent on social money.
I hope this helps and please get back to us with any further questions.
All the best,