NavBar Justified stacking vertically on Mobile - css

Question

My Top NavBar using bootstrap it's fine on desktop but when I browser my website using my Mobile the navbar links appear stacked vertically, instead of horizontal, why is this happening? any clue?
I am using bootstrap, here is my code:
#import 'https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css';
body {
background: black url(Images/image.png) no-repeat center center;
height: 100vh;
}
.footer {
position: absolute;
bottom: 0;
width: 100%;
height: 50px;
}
.navBarLinks {
color: white;
}
.navBarLinks:hover {
color: black;
}
.body-content {} .dl-horizontal dt {
white-space: normal;
}
input,
select,
textarea {
max-width: 280px;
}
<ul class="nav nav-justified navbar-inverse">
<li><a class="navBarLinks">Stuff1</a>
</li>
<li><a class="navBarLinks">Stuff2</a>
</li>
<li><a class="navBarLinks">Stuff3</a>
</li>
<li><a class="navBarLinks">Stuff4</a>
</li>
<li><a class="navBarLinks">Stuff5</a>
</li>
</ul>
//more stuff not relevant
Thank you in advance!

Answer 1

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"/>
<nav class="navbar navbar-default">
<div class="container-fluid">
<!-- Brand and toggle get grouped for better mobile display -->
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" href="#">Brand</a>
</div>
<!-- Collect the nav links, forms, and other content for toggling -->
<div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
<ul class="nav navbar-nav">
<li><a class="navBarLinks">Stuff1</a></li>
<li><a class="navBarLinks">Stuff2</a></li>
<li><a class="navBarLinks">Stuff3</a></li>
<li><a class="navBarLinks">Stuff4</a></li>
<li><a class="navBarLinks">Stuff5</a></li>
</ul>
</div><!-- /.navbar-collapse -->
</div><!-- /.container-fluid -->
</nav>
This is a basic example of what I was talking about...using bootstrap example.
https://getbootstrap.com/examples/navbar/
When you "Run code snippet" open it up using the full page button and then shrink browser to get a better idea.