Hello, @Alessandro,
The issue you are facing is because of this Custom CSS: https://postimg.cc/56cZKPvk you should not have to put the value in minus (-) it always creates responsive issues.
So you have to look for this code under XStore >> Theme Settings >> Theme Custom CSS and change the values as 20px for padding-left and 20px for padding-right and then check back your site after removing the cache.
I tried to log in to your site and gives an access error: https://postimg.cc/NLRNFQ9p
Regards 8Themes Team.