Dear @Robin,
Welcome to the Wefugees Community and thank you for reaching out to us.
In general it should be possible to change from a residence permit according to 16b to a residence permit according to 16a of the German Residence Act.
We had a very similar question here before - you may follow the link for more details and some aspects to consider.
Please also don’t hesitate to get back to us with any further questions.
All the best,
Meike