GP3 flexbox megamenu and foot

I'm testing GP3 in a web with dispatch site library.
With floats the copiright foot not expand.
With flecbox the foot not expand and the mega menu not show well, not show 4 columns only 3.
I paste the code:

@media (min-width: 769px) {
    nav .main-nav .mega-menu {
        position: static;
    }

    nav .main-nav .mega-menu > ul {
        position: absolute;
        width: 100%;
        left: 0 !important;
    }

    nav .main-nav .mega-menu > ul > li > a {
        font-weight: bold;
    }

    nav .main-nav .mega-menu>ul>li {
        display: inline-block;
        width: 25%;
        vertical-align: top;
    }

    nav .main-nav .mega-menu.mega-menu-col-2>ul>li {
        width: 50%;
    }

    nav .main-nav .mega-menu.mega-menu-col-3>ul>li {
        width: 33.3333%;
    }

    nav .main-nav .mega-menu.mega-menu-col-5>ul>li {
        width: 20%;
    }

    nav .main-nav .mega-menu > ul > li:hover > a,
    nav .main-nav .mega-menu > ul > li:focus > a,
    nav .main-nav .mega-menu > ul > li[class*="current-"] > a,
    nav .main-nav .mega-menu ul ul {
        background-color: transparent !important;
    }

    nav .main-nav .mega-menu ul .sub-menu {
        position: static;
        display: block;
        opacity: 1;
        visibility: visible;
        width: 100%;
        box-shadow: 0 0 0;
        left: 0;
        height: auto;
    }

    nav .main-nav .mega-menu ul.toggled-on .sub-menu {
        pointer-events: auto;
    }

    nav .main-nav .mega-menu .sub-menu .menu-item-has-children .dropdown-menu-toggle {
        display: none;
    }