It's always difficult for students to understand idioms. And there are just so many idioms round that it is hard to actually learn enough to be of use.
Certainly, understanding idioms is a more useful goal than actually trying to use them yourself. It's difficult to use idioms because if you get them wrong, no-one will have a clue what you are talking about. And they are often so 'fixed' that it is easy to make a small mistake. For example, you wouldn't say 'I don't have any clue what you mean'. The usual idiom is 'I don't have a clue what you mean'.
So this site might be of value to you as a way of learning/recognising the meaning of a few idioms at a time. Suggestion: even 10 a day might tax your learning ability.