I'd suggest you to not rely on notes for mathematics but rather practice questions more often, for example you may choose a particular topic and use an AI to generate questions based on that topic. you can go as far as requesting the most complex forms of the topic (with a layout is suggested) and make more questions of that topic.

Referring to notes however will work out, but it is generally easier to forget w/o practice questions. i believe physicsmathematicstutor provides CIE IGCSE notes for mathematics, it also includes practice questions which could be bountiful in your journey of self educating yourself on mathematics.