In France, if you want to tell someone that something's not a big deal, not to worry about, they say "N'en fait pas tout un fromage", that is "Don't make a complete cheese out of it". Sometimes abbreviated, at least in this part of the world, to "N'en fais pas".
If you say "Thank you" to a cashier, or to anyone from you have just bought something, you are likely to get the response "It's me". What?
The "c'est moi" is a shortened form of "C'est moi qui vous remercie", that is, with the emphasis used in English, I'm thanking you. At this point, the conversation makes some sense, but for a newcomer to France, it usually takes a few weeks before you hear the full version, and you finally understand those wierd conversations you keep having with shopkeepers.
We do the same thing in English of course. If we say "Don't count your chickens", the follow-on "before they've hatched" is understood, but I wonder if foreigners think the English have some strange kind of superstition about poultry. Same thing with stable doors.
And on the same subject, have you ever tried burning a real candle at both ends? It's a disaster. The wax drips everywhere, you get two big smoky flames, lots of smell, and the candle doesn't last five minutes. But if we work from early morning to late at night, we are "burning the candle at both ends". For this to make any sense at all, there needs to be an unspoken follow-on: "burning the candle at both ends of the day". That is, we need candle light to work by in the morning, and again in the evening.
My candle burns at both ends;
It will not last the night;
But ah, my foes, and oh, my friends
It gives a lovely light!