i'd recommend https://www.refactoringui.com/ to first get build your design "sense". it's fairly simple to build simple UI these days since the default components of design libraries are quite nice.
I read, I think, the first 2 pages of refactoring UI and it was so intuitively brilliant that it somehow unlocked this mental "block" I used to have about design for my side projects. I truly am not exaggerating.