In view of your situation, you really need to learn complement. You should preview advanced mathematics first, and then go back to study high school mathematics when you encounter knowledge points or chapters you don't understand. You can work harder, review your previous knowledge, keep up with the teacher's progress, and even get good grades.

You need to preview as early as possible, but don't be greedy, don't ask for speed, and make progress slowly. I believe you can do it. Come on (? _)? .

I hope my answer can help you.