In general, schools still focus on teaching materials, interspersed with some internship courses. The study of real skills is still in practical work. But school study is still very important. Therefore, I suggest that you study hard at school and learn deeply. First, the working principle of the engine, the common structure of the engine, the common fault diagnosis and maintenance of the engine.

The second is the chassis system, including the troubleshooting and maintenance of suspension, steering and other mechanisms.

Third, automotive electrical systems, such as headlights and stereos.

Fourthly, the design and implementation of automobile modification scheme.

You have learned all the above very well. They all made a lot of money. Personally, I think you should study theory at school for at least one year, then work as an apprentice in the store for one year to verify what you have learned at school, then go back to school for half a year and finally get a stable job. As long as you are willing to study and work hard, you can become an excellent technical expert in two and a half years. The salary is definitely not low. I have such friends around me. I wish you success.