Dear @whatwasmysin,
Welcome to the Wefugees Community and thank you for your question.
I had to make some reserch myself and found the following information (at asyl.net, I translated them to English):
"Persons with unclear nationality must expect that the foreigners authority will ask them to contact the foreign missions of all eligible countries (whose nationality they may have) and obtain confirmation of their (non-)possession of the respective nationality.
In contrast to the determination of refugee status, there is no set procedure for determining statelessness in Germany. However, the immigration authority (Ausländerbehörde) can determine statelessness in the course of deciding on an application for a travel document for stateless persons. However, the determination of statelessness is linked to the final clarification of the person's identity. This means that persons who wish to be recognised as stateless must request confirmation of their nationality from the diplomatic mission of their (possible) country of origin. If no such confirmation is issued, statelessness is assumed.
If the foreigners authority has established statelessness, a residence permit can be issued on humanitarian grounds (Section 25 (5) AufenthG) if statelessness constitutes a permanent obstacle to deportation."
I hope this helps and please don't hesitate to keep us updated or to get back to us with any further questions.
All the best,
Meike