It is only for specific crimes not all crimes and there are exemptions when you don’t have to report the crime in Germany. For example family members don’t have to report if they try to convince the other party not to do it. Priests and other religious figures don’t have to do it. Lawyers, physicians, therapists etc. are also exempted.

It is also only for upcoming not yet accomplished crimes. Crimes already happened don’t have to be reported.

Also it has to be proven that you received the plan in a plausibel manner.