Or change the name at "Discussioni" to another name shorter?

ok @bruno-stano,

I suggest you change the font size. Please delete the code I've provided and put this one:

#wpforo #wpforo-wrap .wpfl-1 .cat-stat-topics, #wpforo #wpforo-wrap .wpfl-1 .cat-stat-posts{
   font-size: 10px;
}

Don't forget to delete all caches before checking. 

Or change the name at "Discussioni" to another name shorter?

Yes, you can edit this phrase and set the value as you like. Just navigate to Dashboard > Forums > Phrase admin page, search this phrase, edit it, and change the value. 

More info here: https://wpforo.com/docs/root/translation/quick-translation-phrases/

IMPORTANT: If you did some change in phrases, please don’t forget to delete phrase cache in Dashboard > Forums > Dashboard admin page.