dropdown nav

HTML

<nav>
			<div id="dropdown">
				<div class="dropdown-wrapper">
					<div class="dropdown-headline">Deutsch</div>
					<div class="dropdown-content">
						<ul>
							<a href="#"><li>EN - UK</li></a>
							<a href="#"><li>EN - US</li></a>
							<a href="#"><li>NL</li></a>
							<a href="#"><li>FR</li></a>
							<a href="#"><li>ES</li></a>
							<a href="#"><li>RU</li></a>
							<a href="#"><li>PL</li></a>
							<a href="#"><li>ZH - CN</li></a>
							<a href="#"><li>ZH - HK</li></a>
						</ul>
					</div>
				</div>
			</div>

CSS

nav {
	height:56px;
	max-width:calc(100% - 60px);
	float: center;
	background: rgb(0, 44, 108);
	font-size: 1em;
	text-transform: uppercase;
	-webkit-border-top-left-radius: 20px;
	-webkit-border-top-right-radius: 20px;
	-moz-border-radius-topleft: 20px;
	-moz-border-radius-topright: 20px;
	border-top-left-radius: 20px;
	border-top-right-radius: 20px;
	padding:0 30px;
	line-height:56px;
}
	nav ul{
		display:flex;
		display: -webkit-box; 
		display: -ms-flexbox;  
		display: -webkit-flex;
		justify-content: space-between;
		max-width:1024px;
	}
		nav ul li{
			-moz-box-sizing: border-box;
			-o-box-sizing: border-box;
			-ms-box-sizing: border-box;
			box-sizing: border-box;
			align-items: stretch;

		}
			nav ul li a{
				height:100%;
			}
			nav ul li a:hover{
				text-decoration: underline;
			}
		nav ul li:nth-child(6){
			width:calc(38.2% + 30px); /* Goldener Schnitt */
			text-align:left;
		}
		nav ul li:nth-child(5):after{
			width:1px;
			background-color:white;
			content:"";
			height:56px;
			position:absolute;
			margin-left:30px;
		}
	nav form{
		position:absolute;
		top:114px;
		right:50%;
		margin-right:-37.1em;  /*wird noch nicht richtig angezeigt; bei kleinen und großen Bildschirm verschiebt es sich um 1px*/
		width:391px;
		height:56px;
	}
	nav input{
		width:170px;
		padding:0;
		margin-top:calc(28px - 1em);
		border:1px;
		height:2em;
		float:right;
		-webkit-border-radius: 5px;
		-moz-border-radius: 5px;
		border-radius: 5px;
		text-indent:0.6em;
	}
	#dropdown {
			display:block;
			width:50%;
		}
		#dropdown .dropdown-wrapper {
				display: inline-block;
				width: 120px;
				position: relative;
				float:left;
		} 
		#dropdown .dropdown-headline {
				height: 100%;
				width: 100%;
				display: block;
				cursor: pointer;
				line-height: 56px;
				height: 56px;
				background: rgb(0, 44, 108);
				color: white;
				z-index: 2;
				position: relative;
				-webkit-transition: background .1s linear, z-index 0s...