Wordpress Menu - custom child dropdown on click with full-width inline items

I'm trying to find a solution for changing Wordpress menu as it shown on example image. I have a problem with design, how to make child menu float from dropdown item? And also how to make it dropdown on click only?

Thanks in advanced!

.nav li ul {
    visibility: hidden;
    z-index: 9999;
    position: fixed;
    width: 100vw;
    left: 0;
    padding: 0;
    text-align: right !important;
    border: none;
    background: #7bc5f7;
    box-shadow: none;
}
.nav li.et-reverse-direction-nav li ul {
    right: 0;
    top: auto;
    background: #bae1fc;
}
#top-menu li li a {
    width: 100%;
}

Example

via Chebli Mohamed