Students majoring in advanced mathematics only pay attention to calculus, which is broad in scope, but not very deep in depth. You only need to borrow the fifth edition of Calculus published by Tongji University from the library, as long as you can understand the basic knowledge and examples, because the professors in the university teach the most basic things, and they teach you how to learn, how to develop problems and how to solve them. Teaching you is just one way.

It's not too important that the senior middle school is not good, because college calculus has little to do with senior middle school.

Don't worry about studying. You can enter the university, which shows that your basic skills are still very good. You can learn well with a little more effort. Please, I am studying, too.