My vocabulary problem

What do you think about you core class study at YUELI? Now I am a level 4 student, in my opinion level is not easy for me. Last week our homework is reading. I think this is very hard for me. I spent a long time to finish this homework, because in this article have a lot of new words. My vocabulary is so bad. I feel frustrated. I always forgot the words and I don’t know how to use them. I have no idea about my vocabulary. Can you give me some advices? I want to improve my vocabulary, but I don’t know how to do.