navigation_bar.css

.topnav {
height: 20px;
width: 100%;
z-index: 1;
top: -80px;
position: fixed;
background-color: #111;
overflow: hidden;
transition: 0.5s;
padding-bottom: 60px;
}

.topnav a {
float: left;
padding: 25px 30px;
text-decoration: none;
font-size: 25px;
color: #818181;
display: inline-block;
border: none;
background: none;
transition: 0.3s;
text-align: center;
}
.dropdown {
	float:left;
    overflow: hidden;
    
}
.dropdown-btn {
padding: 0px 30px;
text-decoration: none;
font-size: 25px;
color: #818181;
border: none;
display: inline-block;
background: none;
transition: 0.3s;
text-align: center;
}

.topnav a:hover, .dropdown-btn:hover {
color: #f1f1f1;
}

.dropdown-content {
	margin: -4px 0px;
    display: none;
    position: fixed;
    background-color: #262626;
    min-width: 160px;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    z-index: 1;
    
}

.dropdown-content a {
    float: none;
    color: black;
    padding: 12px 40px;
    text-decoration: none;
    display: block;
    min-width: 160px;
}


.dropdown-content a:hover {
    background-color: #ff5c33;
}

.dropdown:hover .dropdown-content {
    display: block;
}

.topnav .closebtn {
position: absolute;
font-size: 36px;
margin-left: 50px;
right: 10px;
top: -20px;
box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
}
.active {
background-color: red;
}