Digital Ocean's Command Line Primer is a great intro to using your terminal. It says it's for Linux but it's applicable for Macs, and Windows if you're using something like WSL or Git Bash.
Try to practice using your Terminal to navigate your computer as you're working on other tasks.
GitHub's Markdown introduction introduces using the Markdown language to quickly write simple HTML. Practice your Markdown by writing README.md files for your GitHub repositories. Try to include some headings, lists, images, and maybe even a table.
Execute Program's JS Arrays course
Execute Program is an interactive code learning platform. Their JS Arrays course is a great recap of things you might have already come across, and should also have some interesting new things.
You should be able to get started with a free account—we can get you paid access later when this runs out.
An overview of the fundamental ways you can dynamically change a page with JS.