Suspicions of misconduct or deviations from good research practice should be reported. Some cases are handled by the university, but serious cases are handed over to the National Board for Assessment of Research Misconduct, in accordance with the law. An assessment whether an act or omission is to be considered a deviation from good research practice shall be based on regulation, legislative history and well-established guidelines within the field.
If you are in a situation where you think you may have to report something, you can reach out to the support structures at your university that offer help with research ethics. You can also ask your student union, the ombudsperson for doctoral students, or your trade union for help. You should also be aware that employees at your institution may have an obligation to report suspicions concerning deviations from good research practice.