Idioms/proverbs/clichés can be one of the hardest bits of a language to learn, and they can also be really challenging to translate.
If a Swedish text says, “Don’t sell the bearskin before you’ve shot the bear,” should the translator keep that phrase as is (to retain the Swedishness of the text) or replace it with, say, “Don’t sell your chickens before they’ve hatched” (to make the text fit the English language better)? Or is there another, better solution (a footnote, for instance)? Interestingly, when I go to schools to talk to young people about translation, they are always evenly divided on this topic, with half the people wanting to keep the Swedish phrase and half wanting to replace it with an English equivalent.
When someone recently sent me a link with a list of Swedish idioms, I found it very interesting.
I then found a bunch of similar sites for English-language idioms, and I quite liked this one.
Perhaps you can add additional links for other languages in the comments.