Three phrases that are not quite what they seem:
Un café serré :
Literally: a tightly-gripped coffee:
A strong coffee.
Ne te casse pas la tête :
Literally: don’t break the/your head:
Don’t waste your time.
Tu as peut-être frappé à la bonne porte :
Literally: you have perhaps knocked at the good/right door:
You are perhaps onto something.