Mathematics learning has a strong correlation, and it must be supplemented bit by bit from the foundation. What you have to do is to find out where the knowledge you really lack, and start looking for it bit by bit from the sixth grade of primary school. Don't be bored, you will succeed.
Now imagine yourself as a person who has a stomachache and is eager to shit, but can't pull it out without a toilet. If you find it, you can't lift the toilet lid, you can't lift the toilet lid without taking off your pants, and you can't take off your pants without toilet paper. Now you just need to find what you lack, find this step and do it well. Come on ~