Hello and welcome to the Wefugees Community!
As far as I can see, you are well on the way meeting the requirements for the residence permit according to section 25b, like securing the majority of your livelihood and proving German langauge skills. You would have to apply for this (or the one according to 25a) after the 104c ("Chancen-Aufenthaltsrecht"). For the whole list of requirements (in various languages), you may check Handbook Germany.
Regarding the "Leben in Deutschland" certificate, I wouldn't worry too much since you have registered for a test already - even before the expiration of your current residence permit. In case the results will be delayed, please apply for the residence permit according to 25b already. The immigration office will issue a fictional certificate which allows you to submit the certificate at a later date since you are only waiting gor the results.We discussed a very similar question here before.
I hope this helps and please don't hesitate to get back to us with any further questions.
All the best,
Meike