What happens if i breathe in mould, from food for example? will i get sick? is it harmful?

It depends. Some people are allergic to certain types of mold which may trigger an allergic response. Some molds produce mycotoxins (on spoiled food) which vary in toxicity. Some foods like blue cheese actually derive their distinct flavor from chemicals produced by a friendly mold.( ant it is not toxic at all) Breathing in such material may or may not be a problem.