What should I study? Where did you learn it? ...

You can take the computer secondary certificate, such as vf and C language. There are many training courses in Jinan, such as Sambucus, the Municipal Association for Science and Technology. You can also buy your own textbooks and learn them yourself. You can choose this according to your own situation. In fact, you can ask your brother, sister or teacher, ask them what certificates the employer requires when looking for a job, and then go to school.