Installing Craft CMS on Linux Mint OS?
Nobody is going to be harsh here, so don't worry. The Craft community is a nice place :-)

Sounds like the site root is not pointing to the Craft public accessible folder (the one with index.php). Can you open the URL to another file in the site root? Add a test.txt file for example and try to open it in your browser.

Regarding the .htaccess file: You are using apache, right? .htaccess doesn't work for nginx. Might sound obvious, but you wouldn't be the first to make this mistake. ;-)