I think it's best to start from primary school. Mathematics has a characteristic: the knowledge of each stage will use the knowledge learned before, and almost all of them will be used before college. It's just math I learned in college, and I may not need it in the future. For example, if you want to learn college mathematics, you will use almost all the mathematics knowledge in high school, junior high school and primary school. Junior high school will use 99% of primary school knowledge.

To learn the knowledge of primary school, you only need to do the exercises after class by yourself. After all, go to learn junior high school knowledge.

Then go on to high school.