My visa/residence permit runs out and I am worried that I don’t have an extended visa/residence permit yet.

With the submission of your application file (in Berlin) or request of an appointment (in Potsdam) your visa/residence permit is automatically extended until the Immigration Office takes a decision about your application. In Berlin SERS receives a confirmation mail for each student with an issued case number stating that the student remains legal on the territory and keeps working rights, if they have been issued together with the visa/residence permit, until the Immigration Office takes a decision. This confirmation mail can be requested by the student from SERS and be shown to third partis, such as employers.