Bootstrap 4 - Tabs

Question

<nav id="lang">
  <div class="nav nav-tabs nav-fill" id="nav-tab" role="tablist">
    <a class="nav-item nav-link active" id="nav-en-tab" data-toggle="tab" href="#nav-en" role="tab" aria-controls="nav-en" aria-selected="true">EN</a>
    <a class="nav-item nav-link" id="nav-bm-tab" data-toggle="tab" href="#nav-bm" role="tab" aria-controls="nav-bm" aria-selected="false">BM</a>
  </div>
  </nav>
  <div class="tab-content py-3 px-3 px-sm-0" id="nav-tabContent">
  <div class="tab-pane fade show active" id="nav-en" role="tabpanel" aria-labelledby="nav-en-tab">
    <!-- EN -->
    <!-- END EN -->
  </div>
  <div class="tab-pane fade" id="nav-bm" role="tabpanel" aria-labelledby="nav-bm-tab">
    <!-- BM -->
    <!-- END BM -->
  </div>
</div>