<nav>
		<ul>
			<li><a href="#">Home</a></li>
			<li><a href="#">About</a></li>

			<li class="dropdown"> <!-- Dropdown 01 -->
				<a href="#" class="d-btn">Service</a>
				<ul class="d-menu">
					<li><a href="#">Menu 1.1</a></li>
					<li><a href="#">Menu 1.2</a></li>
					<li><a href="#">Menu 1.3</a></li>
					<li><a href="#">Menu 1.4</a></li>

					<li class="dropdown"> <!-- Dropdown 01 -> Dropdown -->
						<a href="#" class="d-btn">Menu 1.5</a>
						<ul class="d-menu">
							<li><a href="#">Menu 2.1</a></li>
							<li><a href="#">Menu 2.2</a></li>
							<li><a href="#">Menu 2.3</a></li>
							<li><a href="#">Menu 2.4</a></li>
						</ul>
					</li>

				</ul>
			</li>

			<li><a href="#">Contact</a></li>
			<li class="dropdown"> <!-- Dropdown 02 -->
				<a href="#" class="d-btn">More</a>
				<ul class="d-menu">
					<li><a href="#">Menu 1.1</a></li>
					<li><a href="#">Menu 1.2</a></li>
					<li><a href="#">Menu 1.3</a></li>
					<li><a href="#">Menu 1.4</a></li>

					<li class="dropdown"> <!-- Dropdown 02 -> Dropdown -->
						<a href="#" class="d-btn">Menu 1.5</a>
						<ul class="d-menu">
							<li><a href="#">Menu 2.1</a></li>
							<li><a href="#">Menu 2.2</a></li>
							<li><a href="#">Menu 2.3</a></li>
							<li><a href="#">Menu 2.4</a></li>
						</ul>
					</li>

				</ul>
			</li>
		</ul>
	</nav>


<a href="https://youtu.be/HSSFHMWxCuc" target="_blank" class="habibpro">
  VIDEO TUTORIAL
</a>
:root {
  --blackOne : #222;
  --blackTwo : #333;
}
body {
  margin: 0;
  padding: 0;
}

nav {
	position: fixed;
	top: 0;
	left: 0;
	height: 100%;
	width: 250px;
	background-color: #222;
	font-family: 'Roboto Condensed', sans-serif;
	overflow-x: auto;
}
nav ul {
	margin: 0;
	padding: 0;
}
nav ul li {
	list-style: none;
}
nav ul li a {
	text-decoration: none;
	color: #fff;
	display: block;
	text-transform: uppercase;
	position: relative;
}
nav > ul > li > a {
	padding: 10px 15px;

}

nav .d-btn {
	position: relative;
}
nav .d-btn:before {
	content:"";
	position: absolute;
	top: 0;
	right: 0;
	height: 100%;
	width: 40px;
	background-color: #333;
}
nav .d-btn:after {
	content:"\f107";
	font-family: FontAwesome;
	position: absolute;
	top: 50%;
	right: 0;
	-webkit-transform: translateY(-50%);
  -moz-transform: translateY(-50%);
  -ms-transform: translateY(-50%);
  -o-transform: translateY(-50%);
  transform: translateY(-50%);
	width: 40px;
	text-align: center;
}
nav .dropdown {
	background-color: #333;
}
nav .d-btn {
	background-color: #222;
}
nav .dropdown ul.d-menu li a {
	padding: 10px 25px;
	font-size: 12px;
}
nav .dropdown .d-btn {
	border-top: 1px solid #222;
}


/* Habib Pro Tag */
.habibpro {
  position: absolute;
  bottom: 10px;
  right: 10px;
  padding: 15px 30px;
  background-color: #212121;
  color: #fff;
  box-shadow: -2.5px 5px 5px #555;
  font-family: 'Raleway', sans-serif;
  letter-spacing: 3px;
  display: inline-block;
  text-decoration: none;
}
.habibpro:hover {
  background-color: #FFC107;
  color: #222;
  transition: .5s;
}
$(document).ready(function(){
			$('.d-menu').hide();
			$('.dropdown').click(function(e){
				$(this).children('.d-menu').toggle();
				e.stopPropagation();
				e.preventDefault();
			})
		})

External CSS

  1. https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.css

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js