Welcome to the Wefugees Community and thank you for your question.
Yes, that is correct. If your visa application got rejected you can appeal at the administrative court (Verwaltungsgericht) in Berlin within 1 month. The best option might be to hire a lawyer who can support you in this. I am not sure if a lawyer is obligatory though or if you can manage the process by yourself also. However, if you are close to the deadline you may want to send your appeal (Klage) via post or fax already, explaining that you deliver your reasons and arguments soon after getting in touch with a lawyer. You find the contact details of the court here.
Let me link two of our experts as well. Maybe dear @mbeon-Christine or @mbeon-fardeen want to correct me or add some information.
In any case, don’t hesitate to get back to us with any further questions.
All the best,