To understand group theory, the basis for abstract algebra, you dont much to start. The thing that you need most is mathematical maturity since it can get really (for lack of a better term) abstract.

If you want to get better mathematical maturity, i reccomend studying set theory, real analysis; since they are just out of the confort zone of much, and will help you flex your math muscles

EDIT: I just wanted to be extra clear that i havent finished a course in abstract algebra, i learned a bit over a year ago, and it really helped me not feel lost being used to how math is done. I never finished it because I got bored studying it