Css 引导4响应导航栏可折叠按钮

我正在尝试使用Bootstrap4编写一个导航栏，它将显示一个xs屏幕大小及以下的可折叠按钮。我做到了这一点，但是当点击按钮时，导航链接将按钮和品牌名称向下推，并出现在导航栏的上方。我希望它们出现在导航栏下面

有人能帮我吗

    <header>
        <nav class="navbar navbar-default">
        <div class="container-fluid bg-light ">
        <div class="navbar-brand">
          <a id="dominik" href="index.html"><h1>Food, LLC</h1></a>
        </div>

<div class="pos-f-t">
  <div class="collapse" id="navbarToggleExternalContent">
    <div class="bg-light p-4">
     </div>


           <ul id="nav-list" class="nav navbar-nav navbar-collapse">
            <li class="nav-item active">
              <a class="nav-link" href="#">
                <br>Chicken</a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="#">
                <br>Beef</a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="#">
                <br>Sushi</a>
            </li>
            </ul><!-- #nav-list -->


  </div>
  <nav class="navbar navbar-light bg-light d-sm-none">
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarToggleExternalContent" aria-controls="navbarToggleExternalContent" aria-expanded="false" aria-label="Toggle navigation">
      <span class="navbar-toggler-icon"></span>
    </button>
  </nav>
</div>
</div><!-- /.container-fluid -->
</nav>
</header>

用这个更新代码

    <header>
        <nav class="navbar navbar-default">
        <div class="container-fluid bg-light ">
        <div class="navbar-brand">
          <a id="dominik" href="index.html"><h1>Food, LLC</h1></a>
        </div>

  <nav class="navbar navbar-light bg-light d-sm-none">
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarToggleExternalContent" aria-controls="navbarToggleExternalContent" aria-expanded="false" aria-label="Toggle navigation">
      <span class="navbar-toggler-icon"></span>
    </button>
  </nav>

<div class="pos-f-t">
  <div class="collapse" id="navbarToggleExternalContent">
    <div class="bg-light p-4">
     </div>


           <ul id="nav-list" class="nav navbar-nav navbar-collapse">
            <li class="nav-item active">
              <a class="nav-link" href="#">
                <br>Chicken</a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="#">
                <br>Beef</a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="#">
                <br>Sushi</a>
            </li>
            </ul><!-- #nav-list -->


  </div>
</div>
</div><!-- /.container-fluid -->
</nav>
</header>

你不是在做导航栏，因为它是在，另外，你是把两个导航放在彼此里面，这是他们的文档中没有提到的

您可以按原样轻松地从文档中复制导航条形码，然后根据需要更改URL的名称

看看这个