.navbar-dark .navbar-nav .nav-link {
    color: rgba(255,255,255,.8);
}

.dropdown-submenu {
    position: relative;
}

@media (max-width: 768px) {

    .dropdown-submenu .dropdown-menu {
        top: 0;
        left: 100%;
        margin-left: 5px;
        margin-right: 5px;
    }

}

@media (min-width: 768px) {

    .dropdown-submenu .dropdown-menu {
        top: 0;
        left: 100%;
        margin: -9px 0 0 0;
    }

    .dropdown-submenu a::after {
        transform: rotate(-90deg);
        position: absolute;
        right: 6px;
        top: .8em;
    }

}