In fact, learning is not just practice, but understanding. If you can fully understand the knowledge, it will be handy to do the problem. As you said, there are two possibilities. First, you don't understand enough knowledge to do it. Second, you can do it, but you can't figure out the steps. If it is the former, I suggest you read more textbooks and practice after reading the questions; If you are the latter, you should pay attention. It is the problem of being lazy at ordinary times. If you just read and don't write, you will become capable, but you can't take steps. As for the information, I personally don't think it's very important, as long as it's familiar to ordinary people, but you must do it seriously. As long as you can get all one or two materials, your grades will definitely go up. The above is my personal experience, I hope it will help you.