[TOMT] Help me find that movie i saw in samsumg tv plus, please!

Theres a movie that the protagonist is a redhair woman whos a hospital clown, that have a older sister with black hair married with a fisioterapist. The redhair woman and the fisioterapist have a extramarital affair (even before he got married, when she has 14). Things got worse when a new girl is introduced: a redhair from the fisioterapist daughter class got in love with him in a medical appointment. These two (the man and the girl) start to have a casual relantionship (not explicit in the movie) and the police is accionated (perhaps, the detective is a ex husband of the black hair woman). I remember that in the end, the woman knows hes guilty for the crimes so when ther got in a hut (rented, with a large lake, where ther had casual encounters), they have a argument (i think its after s*x), he strangles her (not to death) and go to him home. She just decides to k!ll herself in the lake, her corpse is found and the man goes to jail for murder. The redhair girl start to write a letter to him and the film ends.

This movie also seems to be from Europe (i dont saw it in english)

The family - redhair woman, her sis, the fisioterapist, their daughter, the grandma and grandpa -lives all together.

The redhair woman and fisioterapist work in the same place.