JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
<head>
	<meta name="viewport" content="width=device-width">
	<meta charset="utf-8">
	<title>First Site By PHP</title>
	<link rel="stylesheet" type="text/css" href="style/main.css">
	<link rel="stylesheet" type="text/css" href="style/media.css">

</head>
<body>
	<div class="header">
		<div class="container">
			<ul class="menu">
				<li><a href="#about">About us</a></li>
				<li><a href="">Contacts</a></li>
				<li><a href="#advantages">Advantages</a></li>
				<li><a href="">Chat</a></li>
				<li><a href="">Sign In</a></li>
			</ul>
			<ul class="mob-menu">
				<li><a class="logo" href="">LOGO</a></li>
				<li class="toggle"><a href="#"><img src="data:image/svg+xml;base64,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"></a>
					<ul class="submenu">
						<li><a href="#about">About us</a></li>
						<li><a href="">Contacts</a></li>
						<li><a href="#advantages">Advantages</a></li>
						<li><a href="">Chat</a></li>
						<li><a href="">Sign In</a></li>
					</ul>
				</li>
				</ul>
		</div>
	</div>
</body>
</html>

CSS

@import url('https://fonts.googleapis.com/css?family=Lato|Roboto|Roboto+Mono|Anton|Libre+Baskerville&display=swap');
*{
	margin: 0;
	padding: 0;
}
html,body{
	overflow-x:hidden;
}
.container{
	width: 1050px;
	margin: 0 auto;
}
.first-block h1{
	padding-top: 20px;
	font-size: 50px;
	color: #565656;
	font-family: 'Roboto', sans-serif;
	text-align: center;
	margin-bottom: 150px;
}
.first-block{
	background-image: url("../images/pic-4.jpg");
	background-size: cover;
	background-attachment: fixed;
	background-position: center;
	background-repeat: no-repeat;
	height: 600px;
	text-align: center;

}
ul {
	list-style: none;
}
a{
	text-decoration: none;
}
.header, .footer{
	background: #000;
}

/* HEADER */
.menu{
	padding: 20px;
	text-align: center;
}
.menu a, .col a{
	color: #fff;
	font-family: 'Roboto Mono', sans-serif;
	font-size: 20px;
}
.menu a:hover, .col a:hover{
	color: lightblue;
	text-decoration: underline;
	transition: 1s;
}
.menu li{
	display: inline-block;
}
.menu li:not(:last-child){
	margin-right: 55px;
}

/* ---------- */

/* FOOTER */
.columns .col{
	padding: 0;
	margin: 0;
	display: inline-block;
	width: 300px;
	vertical-align: top;
}
.footer{
	padding: 40px 40px 10px 40px;
	text-align: center;
}
.columns{
	margin-bottom: 20px;
}
.rights{
	color: #656565;
}
.uvins{
	color: #656565;
	font-size: 16px;
}
.uvins:hover{
	color: #EDEDED;
	transition: 1s;
}

/* ---------------- */
.mob-menu{
	display: none;
	height: 30px;
	position: relative;
	width: 100%;
}
.mob-menu .logo{
	color: #fff;
	font-size: 25px;
	font-family: 'Roboto Mono', sans-serif;
	position: absolute;
	top: 13px;
	left: 30px;
}
.mob-menu .toggle{
	position: absolute;
	top: 16px;
	right: 60px;
}
/*.btn{

	color: #EDEDED;
	padding: 20px;
	font-family: 'Lato', sans-serif;
	font-weight: bold;
	border-radius: 15px;
	background: #3186e8;
}
.btn:hover{
	background: blue;
	transition: 1s;
	text-decoration: underline;
*/
/* ABOUT US */

.first-section{
	margin-top: 50px;
	padding-bottom:...