Hi bruno.stano,

It's made by WordPress theme design on our website. The spaces on your website also come from your WordPress Theme page design. We can help you with some small CSS code to remove that space. This is not a wpForo issue, this is a theme issue, so we need your website URL to debug your theme CSS code. Please leave your forum URL.

http://imprenditori.info/community/

Hi bruno.stano,

If I understand you correctly, you'd like to decrease the forum width on the mobile screen. If so, please navigate to Dashboard > Forums > Settings > Styles admin page, put the following CSS code in "Custom CSS Code" textarea, save it, delete all caches and check again. 

@media (max-width: 768px){
.content-area, .inside-footer-widgets>div, .sidebar {
     width: 80% !important;
     margin: 0 auto;
    }
}

It's dont work.. i cant change only the WIDTH on my Attached Photo?