First of all, you should put your mind right. If you hint that it is difficult before you study, it is even more difficult. Start with the basics, starting with the concepts and examples in the book. Stick to it for a while and you will get something.

Definitions can be memorized, but you must understand them before memorizing them. There are concepts. After these understandings, the theorem is deduced. Every theorem is derived smoothly. How to prove that each theorem can be understood from multiple angles, what are the special cases, what are the general cases, etc. )

Then look at the example. Look at the examples smoothly (all examples, why there is this topic, that is, why you want to ask, why you want to solve, whether this solution is useful, whether there is a more general conclusion, whether it can be related to what you have learned before, which theorem or inference is used, and which concept. )

Then look at the exercises. Analyze the exercises clearly (several key ideas, methods, application properties or theorems of each exercise can be summed up in several examples in the book. For exercises with general conclusions, whether the conclusions are useful can be used to solve some difficult problems in exercise books or simplify them. In fact, some difficult problems in exams and competitions are not just the general name of several exercises. ).

That's a bad answer.

Ask if you don't understand.

I hope it helps you.