It is not enough to understand, but just need to practice listening to conversations in English. Imagine If we hear a new English vocabulary, just once. Want to listen to 'em, forget even 5-10 times I still can't remember anyway. It needs to be heard more than credits, we will absorb, understand and recognize immediately, fearing that if it really wants to hear, to listen at least 50-100 times more than we can understand the meaning of English vocabulary as soon as seen.