I just watched the trailer and I hardly understand what they are saying and I live in france my whole life...it's like these awful southern british accents...
shareIt's from Québec... Im from Quebec and it's a French dialect if you will. Lots of expressions in this movie hence the reason why many don't understand the language.
shareIt's not just an issue of France vs. Québec. In Québec there are a range of dialects/accents that generally correspond to social standing.
The main character and her son are of working-class background and that's where the accent is most distinct, including some pronunciations that are archaic elsewhere (like pronouncing moi and toi like "moé" and "toé"), and they use a lot of anglicisms and slang expressions.
On the other hand, there are some characters in the movie (such as the workers in the hospital), who had a more standard pronunciation. They still have an accent but their pronunciation should be easier for European French speakers to understand.