Clarify the allegation from the file first.
Impersonating public authority under section 314 StGB concerns the allegation of assuming an official act or presenting oneself as an authority or official without being authorised. For the defence, precise distinction matters: false official appearance is different from abuse of office by real officials.
At its core, the issue is an appearance of official authority. This may involve claiming to act on behalf of an authority, performing an official act or claiming a power that does not exist.