How to learn UI design in UE

Hi everyone, I’m a graphic designer working in an indie company. I’m on the UI design for an unreal game and I usually create the graphic elements for the games, but now I need to create a working UI in Unreal. The problem is that I don’t know where to start: it seems impossible to find a complete and useful guide for building a UI. I can only find some videos in which they just create simple 4 button main menus, but I need more in depth stuff.

Can someone redirect me to some kind of guide/course about complex ui?