Navbar

<nav class="navbar navbar-expand-lg navbar-dark fs--1 bg-dark"><a class="navbar-brand" href="#">falcon</a><button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarContentdark" aria-controls="navbarContentdark" aria-expanded="false" aria-label="Toggle navigation"><span class="navbar-toggler-icon"></span></button>
  <div class="collapse navbar-collapse" id="navbarContentdark">
    <ul class="navbar-nav mr-auto">
      <li class="nav-item"><a class="nav-link" href="#">Link</a></li>
      <li class="nav-item dropdown"><a class="nav-link dropdown-toggle" href="#" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false" id="navbarDropdowndark">Dropdown</a>
        <div class="dropdown-menu dropdown-menu-right py-0" aria-labelledby="navbarDropdowndark">
          <div class="bg-white rounded-soft py-2"><a class="dropdown-item" href="#">Action</a><a class="dropdown-item" href="#">Another action</a>
            <div class="dropdown-divider"></div><a class="dropdown-item" href="#">Something else here</a>
          </div>
        </div>
      </li>
    </ul>
    <form class="form-inline my-2 my-lg-0"><input class="form-control form-control-sm mr-sm-2" type="search" placeholder="Search" aria-label="Search" /><button class="btn btn-sm btn-light my-2 my-sm-0" type="submit">Search</button></form>
  </div>
</nav>

<nav class="navbar navbar-expand-lg navbar-dark fs--1 bg-primary"><a class="navbar-brand" href="#">falcon</a><button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarContentprimary" aria-controls="navbarContentprimary" aria-expanded="false" aria-label="Toggle navigation"><span class="navbar-toggler-icon"></span></button>
  <div class="collapse navbar-collapse" id="navbarContentprimary">
    <ul class="navbar-nav mr-auto">
      <li class="nav-item"><a class="nav-link" href="#">Link</a></li>
      <li class="nav-item dropdown"><a class="nav-link dropdown-toggle" href="#" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false" id="navbarDropdownprimary">Dropdown</a>
        <div class="dropdown-menu dropdown-menu-right py-0" aria-labelledby="navbarDropdownprimary">
          <div class="bg-white rounded-soft py-2"><a class="dropdown-item" href="#">Action</a><a class="dropdown-item" href="#">Another action</a>
            <div class="dropdown-divider"></div><a class="dropdown-item" href="#">Something else here</a>
          </div>
        </div>
      </li>
    </ul>
    <form class="form-inline my-2 my-lg-0"><input class="form-control form-control-sm mr-sm-2" type="search" placeholder="Search" aria-label="Search" /><button class="btn btn-sm btn-light my-2 my-sm-0" type="submit">Search</button></form>
  </div>
</nav>