I'll go even one step further backwards than SirDice.
Please start a shell. Cd into a directory (which might be your home directory) which contains a least one file. Say the file is called "foo.txt".
Then issue the command: "emacs foo.txt", go into emacs, modify the file (for example add the word "elephant" to it), and save it with Control-X S (or control S or control C, depending on what you feel like).
Do you get any error messages? Does foo.txt contain elephant afterwards?
If it doesn't "just work", we need to debug things, and SirDice's question aim at the likely culprit: Permissions. Which process is running the shell and therefore emacs? Who owns the file? What are the file's permissions?
In your copious spare time: Explain to me the difference between emacs, sublime emacs, and doom emacs. Show me what executables are used for each. I suspect that in the process of explaining this, the problem will become obvious to you.