I may have been misunderstood, sorry for my bad English.
I dont want to "classic" megamenu, i have only categories and subcategoris.
Now all of subcategories are only one line. I would like to change it 2 or 3 columns, so the overall width will be smaller as well.
I tried to add css class second and third levels from your documentation, but nothing helped to me.
by default, width of item element in menu is the same as width of Menu title, but you can increase it if you add width-250 class. You can also add width-300 and width-200"