A list of resources for beginning web developers, in no particular order of importance.
MIT Introduction to Programming unit 1, unit 2, unit 3
Secrets of the Javascript Ninja
Can I Use... CSS Property Support
Animatable Properties Examples
HTML5 Doctor for Semantic HMTL
The Elements of Typographic Style Applied to the Web
CSS animations, transitions, icons... ect. for inspiration
Backend: C++ Go Java
Frontend (fundamentals): JavaScript HTML + CSS (not techincally languages, but we'll skip the semantics)
Frontend (frameworks): Vue React Typescript Sass
Data Science: R Python
Obviously it's better to work on a project that you're passionate about to sharpen your skills, but if you can't think of anything here are a few ideas to get you started:
List of projects from /r/python
Don't forget to save all of your projects to your github. This will become your portfolio during interviews.