Self-study: You can find some BIM training videos online to learn. You can also buy some BIM books to learn. Advantages: wide range, high comprehensiveness and no cost. Disadvantages: learning is not targeted and time-consuming.
Sign up for the training class: Being led by the nose by the teacher can help you avoid detours. Advantages: strong pertinence, generally serving the BIM exam, and short study time. Disadvantages: spending money.
As for which way to study. According to your personal study habits.
Is the training class reliable? . Generally speaking, all the training courses have passed the BIM exam. During training, teachers usually assign homework to students. As for the learning effect, it depends on the individual.
I hope this helps.