If you want to learn “Linux”, I suggest searching for (in order):
A bash tutorial. This is the cli most linux distributions use.
A bash scripting tutorial. This is distinct from the above.
By this time you should be well versed in the cli and bash scripting. Systemd – used by most distributions to manage services and do a variety of tasks – should be your next target.
By now we’re a while further. You should be capable on the cli at this point.
Linux Journey is quite a complete source to get started. It’ll get you up and running, but there’s more.
I suggest you spend some time, once you got the basics, with regular expressions. Bash has regular expressions, grep, and sed have them as well. There are several more commands you’ll want to be familiar with.
Once you’re familiar enough with the commands, I suggest you invest in bash scripting. A good tutorial can be found here. However, it’s by no means a complete one. I suggest checking out the manual page for bash once you’ve finished there.