Removed index.php now all pages with Internal Server Error

I just found the answer.

Firstly, I look out for an apache error log in /var/log/apache2, on the file error.log.1 I found these last lines:

[Sun May 26 22:46:23.694952 2019] [core:alert] [pid 8436] [client ::1:52840] /var/www/html/site2.localhost/public_html/.htaccess: Invalid command 'RewriteEngine', perhaps misspelled or defined by a module not included in the server configuration, referer: http://site2.localhost/wp-admin/edit.php?post_type=page
[Mon May 27 00:08:19.614216 2019] [mpm_prefork:notice] [pid 8418] AH00171: Graceful restart requested, doing restart
AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the 'ServerName' directive globally to suppress this message

Searching for “Invalid command ‘RewriteEngine'”, I found this thread that has an answer to the question:

Look for the file rewrite.load on /etc/apache2/mods-enabled, if you didn’t find the file, run sudo a2enmod rewrite and after restart apache with sudo service apache2 restart.

Now the file rewrite.load appears on the /etc/apache2/mods-enabled directory and I just refresh the browser to everything back to normal.