I graduated Math BSc two years ago and I'm looking to start learning about category theory solo. I started to go through Lang's algebra and although I already learned about groups, normal groups etc in University, I'm having a hard time doing the exercises. Is there any more basic book for this book and other books about category theory (which is the subject I took Lang's for)?
After going through the first chapters of Algebra: Chapter 0 as per @DavidWheeler's suggestion, I can say this answers my question. It has a very refreshing view of the algebra world, and it explains everything using categories. I'm really enjoying it and I'm getting all the review I need.