I just finished watching an excellent YouTube series on BASH scripting in Linux, via Learn Linux TV
https://www.youtube.com/playlist?list=PLT98CRl2KxKGj-VKtApD8-zCqSaN2mD4w
I've been using Linux for more than 20 years, and have been using BASH but never took a formal "course" on it.
Very helpful insights, even for an old grey beard.
Check it out!
(BTW I am NOT being compensated in any way for this post.)