* {
    margin: 0;
    padding: 0;
    list-style: none;
}

.menu {
    display: flex;
    background: blue;
}

.menu > li {
    position: relative;
    padding: 10px 20px;
    color: white;
    border-right: 1px solid white; 
}

.menu li:hover {
    background: oldlace;
    color: black;
}

.submenu {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    background: blue;
    min-width: 200px;
}

.submenu .submenu {
    top: 0;
    left: 100%;
}
.submenu li {
    padding: 10px;
    color: white;
    border-bottom: 1px solid white;
    position: relative;
}

.submenu li:hover {
    background: oldlace;
    color: black;
}

.menu li:hover > .submenu {
    display: block;
}