This is the motto of the German police ("die Polizei: dein Freund und Helfer"). They protect you from danger and fight crime. Policemen and policewomen can be identified by their green or blue uniforms. The police are visible in public every day, on patrol. You can speak to them if you have any concerns. Officers of the criminal investigation department ("Kriminalpolizei") do not wear uniforms; they wear normal clothes. However, they do have an ID card, which they must show you.
The police also have to abide by the rules
The police in Germany have strict regulations by which they must abide. The laws state what the police are and are not allowed to do. For example, they cannot just search a residence. They need a good reason to do this and the permission of a judge, unless someone in the residence is in grave danger, in which case the police can enter without permission.
The police are civil servants of the state in Germany. They serve the general public and cannot be bribed. If anyone tries to bribe the police, they are punished.
In emergencies, you can reach the police at any time by calling 110, free of charge. If you have any questions concerning safety, you can contact your local police.