Schussangst (2003) - Trailer
AKA 'Gun-Shy'
Lukas, a young man doing "meals on wheels" instead of military service, doesn't have many friends and leads a boring life, until he meets Isabella. The fascinating girl soon becomes his best friend, but Lukas learns she has a sexual relationship to her stepfather. Thus, he is obsessed with the idea of delivering Isabella by killing the man...
Director: Dito Tsintsadze
Writers: Dirk Kurbjuweit, Dirk Kurbjuweit, Dito Tsintsadze
Stars: Fabian Hinrichs, Lavinia Wilson, Johan Leysen
https://www.imdb.com/title/tt0379484/