@Mehdifaik

Post the output of error log, use this command to get the last 20 lines:

tail -20 /var/log/nginx/error.log

So we can help you.

Problem in /etc/nginx/Conf.d/ssl.conf
When you change

location / {

root /var/www/;
index index.html;
}

}

to

location / {

root /var/www/**html**;
index index.**php**;
}


}

The page loads as file for download (/var/www/html/index.php)

Hi @Mehdifaik

Can you please post your server block configuration, which should be located in /etc/nginx/sites-enabled/. You can replace your domain with domain.com if you want.
Are you using Let’s Encrypt for SSL or some other certificate provider?