This is a psychological crime drama from Spain, marketed in English as The Hanged Man. (“El Juego del Ahorcado” is the pencil-and-paper game of hangman that we all played when we were kids.)
I could find just one English-language review online, but it offers a good description.
Imagine I Know What You Did Last Summer shorn of its cinematic horror conventions and set in more or less the real world where people live and act normally. You might get something close to The Hanged Man, where two close teenage friends and schoolmates end up killing a common criminal (twice!), hide his body, and spend the rest of the film slowly driving each other mad worrying whether he’s really dead and whether someone will find his body.