If you're interested in more shell stuff, read the Bash Manual. It's not very long and it's quite enjoyable: https://www.gnu.org/software/bash/manual/bash.html

Run all your scripts through https://www.shellcheck.net/ (you can install it locally too) and correct all errors it finds, click the explanation pages to understand why. In future, improve your style so you don't generate errors.

Here's some more I've found useful: - https://tldp.org/LDP/Bash-Beginners-Guide/html/index.html - https://tldp.org/LDP/abs/html/index.html

I would also highly recommend shellcheck (https://www.shellcheck.net/) for useful error messages and warnings!