The German police have two functions: the prevention of criminal offences and the prosecution of crimes. If a crime is committed the police investigate the facts. The police are bound to be objective and neutral in carrying out their investigations and have to look for both incriminating as well as exculpating evidence. The police has to inform the defendant about his rights in the proceedings.
Furthermore the police is obligated to inform you about your rights as a victim.
As soon as the investigation is completed and the facts as well as the suspicion has been finally resolved the police sends a final report to the public prosecutors office. The public prosecutors office then decides whether the proceedings are terminated or continued. If needed the police may be asked to carry out further investigations.