php - Wordpress Drop Down Menu not working properly -

am converting bootstrap theme wordpress theme , followed steps in treehouse , when try add sub menu "lorem ipsum" shows image shown below. want in dropdown list of services. header.php file 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>