It's basically an adolescent angst film featuring a couple of teenagers, Malo and Stéphane, who are far from 'cool' but aspire to becoming so.
In an early sequence the Malo is seen attending the funeral of another pupil. I'm not sure what this added to the overall plot but the humour was certainly a bit tasteless. Malo lives in a dysfunctional family, where dad, Franck, is the house husband, and mum, Eloïse, is a go-getter business woman who thinks a lot more about the next contract with the Chinese than her family. Only the young daughter appears reasonably adjusted.
Stéphane tells Malo about a friend who has a sexy exchange student, with imaginary images to suit, and that he has put his name down for an exchange. Malo hasn't, but the recent death of his friend means that there will be a visiting student without a host family. Again, a bit tasteless. So Malo awaits the arrival of the bus from Germany.
Stéphane gets an Aryan male, who he believes will be a girl magnet, but when Malo finally spots his exchange he sees a Goth female, Sasha, who turns out to have quite an attitude. My favourite line was when she asks Malo's German teacher to speak to her in French as she can't understand his German!
The ensuing story follows a gradual breakdown between Malo's parents while Malo and Sasha, after a period of inane pranks on each other, actually reach an understanding.
This is quite a silly film and I certainly wouldn't recommend it. There are laughs, but the outcome is pretty obvious from the start. As for helping your French, with a preponderance of teen-speak unfortunately I think you'll find a lot of it incomprehensible.