The Refactoring UI book is very good and explains in engineering terms a lot of designer best practises.
I got fairly better over the years and few concepts that might help you.
1) You can learn good design one strategy/approach at a time. Don't believe that are either born a great designer or you can't be one. One step at a time you can become better at it.
2) At the beginning don't try to reinvent the wheel but copy UX or designs from bigger more successful companies like for example Airbnb.
3) Never use pure black #000000 , in the real world pure black doesn't exist, there are very dark colors and some dark grays almost seem pure black but they are actually not
4) Try to have things on the page in proportion to each other, if the top padding is 16px the other left/right/top should probably be 16px too or a multiple of 16px