Wordpress下拉菜单无法正常工作

Am converting a bootstrap theme to wordpress theme and i followed steps in Treehouse And now when i try to add a sub menu "Lorem Ipsum" it shows like the image shown below. I want that in the dropdown list of services. My header.php file is like this

<header>  
  <div class="container top-sect">
    <div class="navbar-header">
      <h1 class="navbar-brand">
        <a  href="<?php echo site_url(); ?>"><?php bloginfo('name'); ?></a>
      </h1>
      <a class="search-form_toggle" href="#"></a>
    </div>

    <div class="help-box text-right">
      <p>Need help?</p>
      <a href="callto:#">800-2345-6789</a>
      <small><span>Hours:</span>  6am-4pm PST M-Th; &nbsp;6am-3pm PST Fri</small>
    </div>
  </div>


  <div id="stuck_container" class="stuck_container">
    <div class="container">   
    <nav class="navbar navbar-default navbar-static-top pull-left">            

        <div class="">  
          <ul class="nav navbar-nav sf-menu" data-type="navbar">
          <?php wp_list_pages(array('title_li' => '')); ?>
          </ul>

        </div>
    </nav>  
    <form class="search-form" action="http://static.livedemo00.template-help.com/wt_54725/search.php" method="GET" accept-charset="utf-8">
      <label class="search-form_label">
        <input class="search-form_input" type="text" name="s" autocomplete="off" placeholder=""/>
        <span class="search-form_liveout"></span>
      </label>
      <button class="search-form_submit fa-search" type="submit"></button>
    </form>

    </div>

  </div>  
</header>