Like first time I try to self study before the lecture then I make notes to have better understanding and comprehension.
Then,I have notes during lecture , else I will feel sleepy and not able to remember things .
Then, again after coming back from lecture I make notes because I usually come with better insights and understanding.
Now, again while revising text I get new things and understanding while browsing and reading online sites and various university lecture notes.
But, now I am not able to understand how should I revise and remember things from various multiple sources.
Prepare for exams and scholarship exams.
I will include what I find works best for me (this is probably not universal for everyone so take it with a pinch of salt).
Maths is no different to any other skill and you learn by doing. If you have a reading list in your course, this is often useful to find a rich source of exercises. Do many problems, even if you don't properly write them all down. You will get much better at a subject by solving problems than by memorising the proofs of all the important theorems. If your course does not have a reading list, you can usually find good recommendations for every subject online.
However, you might be expected to just memorise some proofs. What I usually do for this is typing them in LaTex. Wanting them to look nice usually makes me think a lot more about them, so that I eventually come up with the nicest method while keeping it concise. You will also have a really good set of notes because you will have made them and it will be easier to study everything.
Finally, if you have the time and motivation, I recommend reading a bit further on every topic you study, moving to slightly more advanced content. This will make all of the previous content look easier in comparison as well as force you to understand well everything before it.