I am taking a course in Lie Theory and Theory of Representations this year, where starting from the second lecture, Lie Theory is heavily bundled with Theory of Representations.
It is pretty much a series of theorems, lemmas, corollaries, etc., and I hardly understand any of it, because it is quite abstract, dense, and stacks up very quickly. It seems that the course is research journal level, not graduate level.
I have a high GPA, and did not have issues with courses before.
What would be a good strategy to tackle a course like this?