Untrue statement of fact about you: examine defamation under Section 111 StGB.
Where a person is accused, in a manner perceptible to a third party, of dishonourable conduct or conduct contrary to good morals that is capable of lowering them in public opinion, defamation under Section 111 StGB comes into question. It is in principle a private-prosecution offence that the injured party must pursue themselves.
From a legal perspective the precise classification is important: is it a verifiable statement of fact or a value judgement? That determines which offence applies and which steps are sensible.