Learning a new OS. Wow, I am still learning new Linux tricks every day, after 20 years!
A good start is an old site,
TLDP.org , The Linux Documentation Project. The Guides, especially
Introduction to Linux - A Hands on Guide, and
GNU/Linux Command-Line Tools Summary . These old, but thorough guides, will give you an idea about what you can do with a few commands, and a starting point into how Linux is screwed together.
Remember, in Linux, every command in a program is just a text file - which can be edited, and the basic Linux philosophy is that a command should do only one thing, but do it well, and you should be able to use the result as input for the next command.
https://en.wikipedia.org/wiki/Unix_philosophy.
For the fun of it, in a terminal window, you just press the Tab key twice - tab-tab, and see how many possible names of comands/programs that turn up. In my tahr, it says 2238. Not much, when Debian has more than 60.000 programs to download. You have access to all of them in Stretch7.5.
You may enter a, and then tab-tab to get a list of all commands/programs beginning with a.
Those are interesting lists to browse, and for each of the commands/programmes, once you have the full name entered, you can usually tab to get a list of options, or use command/programname -h, or command/programname --help.
You may be used to running GUI programs only, but I would advice you to get an insight into using the terminal window now and then, soon you'll find that a line with a few commands, does exactly the same as a big GUI program does.
Don't hesitate to ask 'silly' questions, it is the way most of us have learned a little Linux!
![Laughing :lol:](./images/smilies/icon_lol.gif)