JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="topMenu">
				<li><a href="#">Автосалон</a></li>
				<li><a href="#">Путешествия</a></li>
				<li><a href="#">История</a></li>
				<li><a href="#">Разное</a></li>
			</ul>

CSS

.topMenu{
	position: absolute;
	right: 0;
	top: 0;
	background-color: #000;
	padding: 10px 12px 10px 0;
}
.topMenu li{
	display: inline;
    position: relative;
	margin-left: 20px;
}
.topMenu li:first-child {
    margin-left: 0;
}
.topMenu:first-child:before {
    content: '';
    position: absolute;
    top: 0;
    bottom: 0;
    left: -40px;
    width: 0;
    border-bottom: 40px black solid;
    border-left: 40px transparent solid;
}
.topMenu li a{
	color: #fff;
}