Sometimes the default content of Joomla .htaccess file, or possibly changes you have made to it while trying to make it work, can result in your site being broken. It will then only display an error page showing a 500 error, or another.

To get your site back, simply rename the .htaccess file in your site root directory to something else (like htaccess.txt, as it was named initially).

Then you can try again with a different content for .htaccess file.