Consider phrasal verbs like "shut up", "get lost" or "kick off". Knowing what the parts mean doesn't let you understand the whole.

In your native tongue you take these for granted, but in a second language you have to learn that the sum is more (or different) than the parts.

They don't get into enough learning lists, and from my perspective, they are great additions to word games because the more transparent compounds are unique and legit words that can more than double the accessible vocabulary.