There is a short non-graphic oral sex scene near the beginning of the film, two shorter sex scenes with more nudity near the end, and a longer more graphic rape scene at the mid-point of the film. All of these scenes are between an adult and teenager with a teacher/student dynamic.
This is subject to personal interpretation but while the protagonist survives, he loses nearly everyone he is close to and is traumatized by his experiences.
(Major spoilers) The antagonist of the film systematically stalks and murders all of the relatives of the man she blames for her mother's death, including grooming and raping his teenage grandson before attempting to also murder him.
Mrs. Jung (the teacher), chokes a student to death in the library when the student becomes suspicious of her. Jonas is almost drowned during the climax of the film.
Jonas is raped multiple times during the film by his teacher, including one occasion where she breaks into his home in the middle of the night and sneaks into his bed while he is asleep.