Running or investing in a restaurant alone cannot grant you the qualification for applying for visa for self-employment. You can be better consulted if you provide more information, such as knowing if partner runs a company or any other business. Otherwise, you can consider opening and operating your own company in Germany in order to obtain a visa for self-employment. The minimal capital is 25,000 euros.
How can I invest in my friend’s business and apply for the German resident permit?
My friend (a German citizen) runs a small restaurant in Berlin. I would like to invest in the restaurant, help him expand it and become a partner of the business. Can I use this business to apply for a German resident permit for the purpose of self-employment? Are there any requirements on his business?