This film of end of 80s…beginning of 90s. I remember the final of that film. The young girl is looking for her boyfriend. She comes into the flat. A lot of teenagers sleep on the floor in that room. And her boyfriend is in another room with another girl. She falls down on the armchair and gets asleep. And one of teenager awakes. He sees the girl, comes to her and begins fuck her. The girl awakes and the film is over.
Sounds like “Kids”; not French, but maybe you saw it dubbed into French? https://www.imdb.com/title/tt0113540/?ref_=fn_al_tt_1
It is “Kids”! Yes! I did not know that is not French! Thank you!
Thought so. Solved!