Simply put, joining classes can improve your English quickly, learn more scientific and systematic learning methods, and get the help of teachers. From this point of view, it is worth a try to sign up for a training class.

In addition, it depends on your own self-control. If you have strong self-control, many things can be taught by yourself online now.

Recommending an app is not an advertisement. China University has a large number of online courses, including many courses from top universities. You can go and have a look if you are interested. I think you can learn a lot there.