It's easy to code when I copy someone else on a screen but am I truly understanding what I am being taught?

This is the first step, if you are understanding other's code, then yes, one day you will be able to write a complete program yourself.

I went through the course you're taking, it's good but I don't think so it's good to learn JS before you completely master HTML and CSS.

I would suggest to take this course first, a complete course where you will be developing your own website from scratch. This course helped me understand some basic concepts that I never knew.

And don't give up please. I dived into this coding stuff 6 months ago at the age of 29 and 7 months and I have been facing the same issue while learning PHP but I know, once I master this language, I will have a whole new world to explore!