Welcome to the Wefugees Community and thank you for your question.
When I am not mistaken, you can apply for the permanent residence permit (Niederlassungserlaubnis) after 5 years of having a temporary residence permit in Germany (i.e. §30/§31 AufenthG). Additionally, you have to be independent from social benefits and need to prove a sufficient level of German. For more details and the full list of prerequisites please have a look at, for instance, this website (explaining about the application process in Berlin though).
Am I right on this, dear @mbeon-Bernd or @mbeon-Ruth?
In any case, please don't hesitate to get back to us with any further questions.
All the best,