Make mega menu full width of users screen

Hello,

Try to add the next code in Theme Options > Theme custom CSS:

.header-wrapper .et_b_header-menu .menu .item-design-mega-menu.menu-item-has-children {
    position: static;
}
.header-wrapper .et_b_header-menu .item-design-mega-menu .menu-static-block.nav-sublist-dropdown {
    margin: 0 !important;
    left: 0 !important;
    right: 0 !important;
    width: 100%;
}
.header-wrapper .et_column {
    position: static;
}

or for “Apple” menu item only:

.header-wrapper li#menu-item-5346 {
    position: static;
}
.header-wrapper li#menu-item-5346 .nav-sublist-dropdown {
    margin: 0 !important;
    left: 0 !important;
    right: 0 !important;
    width: 100%;
}
.header-wrapper .et_column {
    position: static;
}

Regards