<nav class="navbar navbar-expand-lg navbar-dark bg-primary">
  <div class="container-fluid">
    <a class="navbar-brand" href="#">Brand</a>
    <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#main_nav">
    <span class="navbar-toggler-icon"></span>
    </button>
    <div class="collapse navbar-collapse" id="main_nav">
      <ul class="navbar-nav">
        <li class="nav-item dropdown">
          <a class="nav-link dropdown-toggle" href="#" data-bs-toggle="dropdown"> Menu item </a>
          <ul class="dropdown-menu">
            <li><a class="dropdown-item" href="#"> Dropdown item 1 </a></li>
            <li><a class="dropdown-item" href="#"> Dropdown item 2 </a></li>
            <li><a class="dropdown-item" href="#"> Dropdown item 3 </a></li>
            <li class="has-submenu">
              <a class="dropdown-item dropdown-toggle" href="#"> Dropdown item 4 </a>
              <div class="megasubmenu dropdown-menu">
                Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
                tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
                quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
                consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
                cillum dolore eu fugiat nulla pariatur. 
              </div>
            </li>
            <li class="has-submenu">
              <a class="dropdown-item dropdown-toggle" href="#"> Dropdown item 5 </a>
              <div class="megasubmenu dropdown-menu">
                Excepteur sint occaecat cupidatat non
                proident, sunt in culpa qui officia deserunt mollit anim id est laborum. 
                Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
                tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
                quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
                consequat.
              </div>
            </li>
            <li><a class="dropdown-item" href="#"> Dropdown item 6 </a></li>
          </ul>
        </li>
        <li class="nav-item"> <a class="nav-link" href="#"> Menu item </a> </li>
        <li class="nav-item"><a class="nav-link" href="#"> Menu item </a></li>
        <li class="nav-item"><a class="nav-link" href="#"> Menu item </a></li>
      </ul>
    </div>
    <!-- navbar-collapse.// -->
  </div>
  <!-- container-fluid.// -->
</nav>