Hi Hugo,
Please use this Custom CSS - should help by now
.sp-megamenu-parent .sp-dropdown .sp-dropdown-inner {
padding: 10px 0;}
.sp-megamenu-parent .sp-dropdown li.sp-menu-item
{padding: 0 10px;}
.sp-megamenu-parent .sp-dropdown.sp-dropdown-main.sp-menu-right
{left: -30%;}
.sp-megamenu-parent .sp-dropdown li.sp-menu-item > a
{padding: 5px; font-size: 15px;}
but can you check megamenu for that menu item, maybe there is option to align menu to left. I don't have that template working copy to check.