<div class="dropdown-transport">
      <a href="#" class="dropdown-bt">Транспорт</a>
      <div class="dropdown-content">
            <a href="#">Link 1</a>
            <a href="#">Link 2</a>
      </div>
</div>

.dropdown-content {
  display: none;
  padding: 10px;
}
.dropdown-bt:focus + .dropdown-content {
    display: flex;
}