Understanding idiomatic expressions in French can be tricky for students who know some French already. Here are a few common expressions that can cause confusion:

1. “Avoir le cafard” - This means "to feel down." It can be confusing if you don't know what it really means.

2. “C'est la vie” - This translates to "That's life." It seems simple, but it can express complicated feelings.

3. “Être dans le pétrin” - Literally, this means "to be in dough," but it really means being in a tough situation. This can also confuse learners.

The challenges come from the cultural meanings and situations behind these phrases. Plus, many learners find it hard to pronounce and use them in conversations.

Here are some tips to help you:

• Talk with native French speakers.
• Watch French movies or listen to French music.
• Use language apps that focus on idioms often.

By working on these areas, learning French can become easier and more fun!