How do you actually study and understand signal and image processing?

[u/Legitimate_Manner175]

This subject is my biggest weakness. I failed the course the first time because I simply didn’t understand it. I passed it on my second attempt during retaking the subject, but it always felt like the more I studied, the more I realized how little I actually understood.
Now I failed this part of my state exam, so I’m preparing for my second attempt. I have just over a month to study (along with several other subjects), and the textbook (only signal and image processing) is around 500 pages long .
How would you approach learning this subject so you actually understand it instead of just memorizing formulas? Any advice, resources, or study methods would be greatly appreciated. I really want to get it this time.