Peut-être

After having sex with his girlfriend Lucie (Pailhas) in a bathroom, Arthur (Duris) discovers that a ceiling panel is a time portal to the Paris in the future, although it appears more like a sun-baked desert city by that point. There he meets an old man named Ako (Belmondo) who turns out to be Arthur's son. Ako attempts to persuade Arthur to impregnate Lucie so that he can exist in this future. (Wikipedia)