Nice to hear from you again.
A Führungszeugnis is issued by your local Bürgeramt/Bürgerbüro/Bürgerservice (the name might vary depending on the city you live in). Usually it should take around 2 weeks to receive it via post. But this also might vary depending on your location. If you've been waiting for six weeks already, you should get in contact with them and ask them about your case.