You may work as a freelancer in Germany if the profession is on the list declared by German authorities.
If you wish to work as a freelancer, you must prove that you have your own capital to finance the projects that you will undertake. To apply, you must also provide proof of documents, such as licenses, that you are competent to carry out this work on your own. You must also demonstrate that you may meet your own retirement needs.
In the first application, a maximum of 3-year visa is issued, and then you may extend the duration if your business idea has been successful and if you may cover all the costs for you and your family members.