Dear @Taka,
Welcome at Wefugees and thank you for reaching out to us!
We just answered the very same question here a few days ago (please check it out for additional details) where my colleague explained:
"As long as you apply for the permit 25b before your permit 104c expires, then your status automatically continues until the Ausländerbehörde makes a decision on your application. The paper they issue which confirms this continuing status is called a 'Fiktionsbescheinigung'.
The Fiktionsbescheinigung allows you to continue to work. You do not have to apply for an additional work permit or anything else."
I hope this helps and please don't hesitate to get back to us with any further questions.
All the best,
Meike