Best courses to study UX/UI [closed]

I work mainly as a backend developer, but I do frontend for my projects. While I can code in JS (react, vue), I can't make any of my interfaces to look nice. All of them are clunky and have terrible UX.

Are there any good courses, certifications or study materials that could help me to learn Mobile and Web Design/UI/UX? Maybe any recommended way to train my "intuition"?