Whether it works or not, it must work. But as for failing, on the one hand, it depends on the teacher (the teacher is very important, but there are not many real famous teachers), on the other hand, it depends on your own actual situation (20 people are recruited for a position, and a buddy took 58 exams, anyway, it is estimated that you can't pass) and the degree of effort, and see if you can devote yourself to practice, insist on after-school practice and improvise. Regarding the refund, some regulations can refund money, while others can't. For example, if you don't take the exam yourself, you won't have money to return it.
In fact, many training institutions do not recommend people to sign up for this kind of agreement class. Candidates have risks, and training institutions also bear risks. It is better to accept thousands of dollars from other classes.