The tutorials from Catlike Coding are an excellent resource for learning Unity programming structure and foundational concepts. Their Basics Tutorials in particular are fantastic for building comfort and confidence so you don't feel lost. While some advanced functions may require modification for U# (Udon Sharp) compatibility, they serve as a superb reference for structuring your code and creating robust, functional products.

Natty GameDev's FPS Shooter tutorials is a great way to grasp the power and flexibility of classes. A key takeaway from this series is learning how to implement custom, in-editor menus, which greatly simplifies the process of changing parameters during development.

I cannot rate 3D textures as a resource highly enough. They offer extensive free textures that are easy to set up in unity. They also offer higher resolution textures with a membership. I can spend hours comparing their textures for different scenes and I think you should check them out!