So how can I as a new user make sure to have the most secure machine as possible?

Shut the computer down. That's it; computer as secure as possible.

Otherwise, if you actually want to use your computer, google for "threat model" first.

But generally: use an adblocker in your webbrowser, don't execute random commands/tools from the internet before you know for sure what you're doing, update stuff now and then and make backups.