Hi! I've always been interested in math and physics, since I was a kid, but like many of us, life takes us to different places, so I ended up pretty far away from those subjects. My background in mathematics is a pretty good understanding of high-school level, and ever since then, I haven't been exposed to anything beyond that. Perhaps the only exception being Linear Algebra, due to my career. Recently I have decided to pursue my interest in physics as a hobby, and so started reading a lot about GR and QM, and anything related to those. While I can grasp the general concepts, I quickly found myself lost in the maths and unable to get past that. So, I decided to take a break from the physics studies and literature, and instead focus a bit on my maths background. My issue is that each time a pick a subject, I find it requires some previous subject that I also lack understanding of, and then that also requires something I wasn't aware of, so I kept going back, and am now at a place where I have a simple plan to progress in subjects up until GR. Has anyone been in a similar situation and has any sort of tips, or perhaps has a road-map of the different subjects to tackle they could share? My current method has been to read books, mostly I cherry pick chapters related to a subject in many different books, as well as following youtube lessons, and whatever else I can find. Sometimes the differences in notation are quite confusing, but nothing too bad. One problem I have is that I don't really know how well I really understand things. When reading the books things seem obvious, and simple, but I can't help not feeling very confident about my understanding... I was wondering if someone could recommend some exercise books, preferably with explanatory solutions, on the various subjects of basic post high-school mathematics... Thank you!