Of course, it is useful to apply for classes, but there is no inevitable conclusion about whether you can apply for classes. Just because of people. If you have a good foundation, good self-control and strong learning ability, you can actually enter the class without signing up. If students with poor foundation, poor learning ability and self-control ability still suggest to sign up for classes. After all, it is better to follow the teacher and have someone to lead the way than to ponder for themselves. In terms of courses, I suggest using online courses. First, online courses are cheap, second, learning is convenient, and third, teachers are relatively stable. As for which online course to choose, you can compare and choose from the following aspects. On the one hand, you can look at word of mouth online and see how people who have used it reflect it; Secondly, you can find an audition class to listen to and see which class you like. After all, everyone has different preferences and wants to fall in love. Some like to be fat and some like to be thin, so we can't generalize. What you like is the best. Third, depending on the length of class hours and the long preparation time, you can choose longer courses, which are generally more detailed and shorter. Such courses generally focus on the key points.