Bootstrap 4 I'；我试图在小屏幕上保持我的导航链接，它们以900像素的速度消失

我试图保持我的导航链接可见我尝试了一个下拉按钮，不会下拉。。。我安装了popper js，但仍然没有安装

我把按钮拿了出来，因为我更可能只是想让链接水平地显示在屏幕上。可能吗

 <nav class="navbar navbar-expand-lg fixed-top ">  

<div class="collapse navbar-collapse " id="navbarSupportedContent">    
    <ul class="navbar-nav mr-4">
     <li class="nav-item">
     <a class="nav-link" data-value="home" href="#home">Home</a>        
  </li>  
      <li class="nav-item">
      <a class="nav-link" data-value="about" href="#about">About</a>        
  </li>  
     <li class="nav-item">
     <a class="nav-link " data-value="photography"href="#photography">Photography</a>    
 </li>
     <li class="nav-item"> 
     <a class="nav-link " data-value="blog" href="#casestudies">Case Studies</a>         
</li>   
     <li class="nav-item">  
     <a class="nav-link " data-value="team" href="#projects"> Projects</a>       
</li>  
    <li class="nav-item"> 
    <a class="nav-link " data-value="contact" href="#">Contact</a>       
</li> 
    </ul> 
  
    </div>
  
    </nav>

试试这个导航条