As developer, designing from scratch has been hard for me always. What worked for me when I wanted to learn about some new design software is to start getting some existing work from some designer. You can download some templates and start discovering how people use this softwares. You can have some design and start playing with it. Changing properties to elements, changing sizes, colors, borders, adding your own elements based on another ones, ...
I recently updated my tools. I was on Fireworks CS5 for a loooong time. This software worked for me very well, simple, easy and very effective. Recently tryied Figma and Adobe XD and definitely, XD is my favourite one. It seems very simple for me and fits my needs very well having just the necessary features. I find easy to move from my mockup to a real web. If you are on MAC, I think Sketch is the more generalised option.
Regarding resources, Refactoring UI is a great guide to improve designing skills for developers non designers.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.