JSFiddle - React, Tailwind, and code Playground

HTML

<nav class="nav">
	<ul>
		
		<li  class=""><a href=#>ÚVOD</a></li>
		<li  class="">
			<a href=#>kurzy</a>
			<ul>
	        	<li ><a href="#">test</a></li>
	        	<li ><a href="#">test</a></li>
	        	<li ><a href="#">test</a></li>
			</ul>	
		</li>
		<li  class="#"><a href=#>ÚVOD</a></li>
		<li  class=""><a href=#>ÚVOD</a></li>
		<li  class=""><a href=#>ÚVOD</a></li>
	</ul>
	
</nav>

CSS

.nav ul, .nav li {border:1px solid #f00; background:#eee;} 

.nav{
	font-family: 'PT Sans', sans-serif;
	
	box-shadow: 		0 1px 6px rgba(0,0,0,0.3);
	-moz-box-shadow:    0 1px 6px rgba(0,0,0,0.3);
  	-webkit-box-shadow: 0 1px 6px rgba(0,0,0,0.3);
  	text-transform: uppercase;
  	background-color: white;
	
	
	width: 100%;
	height:70px;
	padding: 0;
	line-height: 70px;
	vertical-align: middle;
}

.nav  ul {
	float: right;;
	list-style: none;
	text-align: center;
	padding: 0;
	margin: 0;
	
}

.nav > ul > li {
	
	width: 120px;
	border-bottom: none;
	height: inherit;
	font-size: 1.4em;
	
	display: inline-block;
		
  
	font-family: 'Oswald', sans-serif;
	font-size: 1.2em;

}

.nav a {
	
	text-decoration: none;
	color: black;
	display: block;
	transition: .3s background-color;
}

.nav > ul > li:hover {
	float:none;
	clear:both;
	background-color: #005f5f;
	border-bottom: 5px solid #ff0000;
}


.nav  > ul > li > ul{
	
	display: none;
	position: absolute;
	width: 100px;
} 

.nav  > ul > li:hover > ul{
	display: block;
}