Hi, I am a high school student, and I am trying to learn set theory (it's not for school - independent study; I love it). I have a book (Takeuti/Zaring Introduction to Axiomatic Set) Theory and I am going through it, but I feel like I'm going way to slowly (after trying to go through it for 2 months now and countless hours, I'm only just completed chapter 8 on ordinal arithmetic out of 20 chapters or so. And this is like for 1.5 hours a day and the first 4 chapters you can finish in a day.). Furthermore, I feel like I don't quite understand the idea of ... say, an isomorphism. Like, I could explain to you exactly what it is, but I feel like I am just spitting out the definition, and that I don't have a true understanding of it. Plus, sometimes I get really stressed for some reason when I do it for more than 2 hours. It's a problem because none of my teachers can really help me with it. What do you recommend?