I have a similar experience with you. After studying Apple Tutorial, I also read Apple's official Swift tutorial called "The Swift Programming Language", but the document is more engineering and there are many places that are difficult to understand. But in the process of reading, you can think about what Apple's purpose is. After that, I learned the lectures for the Spring 2021 version of Stanford University's course CS193p. In my opinion, the course explain SwiftUI in more detail. It not only talks about UI layout, but also about MVVM design pattern, animation, etc. I hope my above experience can help you.