Dear @VIDYA AL MAHMUD,
thank you for sharing your situation with us in the community.
as for your question please follow the link below- as a similar question has been answered in the past:
In your particular situation if are still working you should first apply first for an Aufenthaltserlaubnis and once you have that you can apply for a permanent residency.
If you already have an Aufenthaltstitel then you can already apply and it should be granted. Do you have the Master Degree from Germany?
I hope this can guide you if you still need more clearifications please let us know.