Criminal complaint
Domestic violence is punishable violence.
Domestic violence includes a number of acts sanctioned by criminal law that are prosecuted ex officio due to the public interest.
A report can be made by you as the victim - or by anyone else. This can be done in writing or verbally at any police station or public prosecutor's office. In the event of a police operation, the police may file a criminal complaint on their own initiative.
After the report, the authorities will begin their investigation. As the victim, you are the central witness. The police and/or the public prosecutor's office will most likely question you personally in the course of the investigation. Every witness to a criminal offense is obliged to testify, unless there is a close family relationship (right to refuse to testify). Following the investigation, the public prosecutor's office decides whether to open proceedings or whether to discontinue them, e.g. due to a lack of evidence.
As a general rule, the earlier the investigation can be started, the better the evidence and therefore the chance of prosecuting the offender.
You can read more about the process and your rights in criminal proceedings here:
http://www.polizei-beratung.de/opferinformationen/
In the case of rape/sexual assault, you can find further information at
https://www.frauennotruf-muenster.de/sexualisierte-gewalt/anzeige-erstatten-ja-oder-nein/
You are considering whether you want to press charges or whether you should be questioned as a witness to a police report.
You may be confronted with conflicting feelings - this is understandable.
You can seek advice to gain clarity about what you can and want to do.
You can find information on advice centers here.