I believe on one of your other threads, I have posted a link to a thread where I shared the long-term strategies I used when studying - this includes giving yourself a timetable so you can manage your time more effectively and give yourself a routine that will help you to ensure you don’t have outstanding homework.
These aforementioned strategies may be of some use, but as evidenced by your post, everyone has their own unique learning style. And if said strategies don’t work, you now one way not to go about self-teaching, which narrows down the search to find the optimal method.
Clearly, you are not a bad student. You have seen tangible progress with your maths following a very pragmatic attempt to align your studies outside of school more towards methods you are aware work. I expect a similar approach can be applied with your other subjects and you will see similar progress made.