Your options:

You are working as a researcher in Germany and would now like to set up a company that is related to your research activities? For this purpose, you must apply for a residence permit for self-employment at your competent foreigners authority. 

Among other conditions, these are the requirements you must meet:

• You can secure your livelihood.
•  If you are over the age of 45, you must have proof of adequate retirement provision.

Questions regarding self-employment in Germany: 

• Find out about the available special consulting and information services in the "Advisory services" section.