These commands will help you get started. To make them really useful, you will need to do some more reading and research.
You should learn next about file permissions, which are settings you can attach to files and directories specifying which users may interact with those files and directories as well as what may be done with the files and directories. To learn about this, you will also need to learn about user accounts and how they are used both by human users of the system and even programs and automated processes./
After that, spend some time familiarizing yourself with the Linux file system. There are a set of standard directories and common files that appear in the same locations across machines running Linux. Knowing where to look for something and what to look for will be of great assistance, especially if you take the time to learn before something goes wrong that you need to fix.
Consider learning about different command shells. The most common defaults are bash and dash, both of which will use the commands I describe here, but there are others. Each shell includes features that you may discover you prefer or that are better suited to your situation. Consider tcsh, ksh, and zsh.