Maybe I wasn't paying attention but:
1) Who and why was the car keyed? and
2) What were the papers Grégoire burned just before ... (to avoid a spoiler)?
The cure for boredom is curiosity. Unfortunately, there is no cure for curiosity.
The car-keying scene was from a film-within-a-film, one that was playing onscreen while the characters watched (perhaps one by Darezhan Omirbaev?).
I don't believe we're meant to know what Grégoire was burning.
At first, I thought Gregoire had burned papers relating to his son by his former lover, but then we find out that his wife knew about the son. Maybe the audience isn't meant to know what he burned and instead we can speculate that he had a dark secret that contributed to "what happened" (trying to avoid spoiling it for those who haven't seen it yet).
shareHe took at least 2 letters from the glove compartment of the car & one had an 'airmail' envelope. One other in a brown envelope looked like it may have been some kind of 'bill' or account. The others we couldn't see but looked like more envelopes. I would say it was something he didn't want his family to find after his death, but we don't know quite what.
There is also a 'goof' in the credits of the film. The guitar piece of music which was played as the family is driving out to holiday is an English standard called 'Greensleaves' . In the film credit it's shown as Blue Sleaves
^The above poster also "goofed". The name of the music is spelled "Greensleeves".
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