Modal over another modal

Hi,

I need your help, I want to display a modal over another one but the overlay(mask/backgraund) don't apply over the first one

My code is below:

<!-- Button trigger modal -->
<button
  type="button"
  class="btn btn-primary"
  data-mdb-toggle="modal"
  data-mdb-target="#exampleModal"
>
  Launch demo modal
</button>

<!-- Modal -->
<div
  class="modal fade modal-sm"
  id="exampleModal"
  tabindex="-1"
  aria-labelledby="exampleModalLabel"
  aria-hidden="true"
>
  <div class="modal-dialog">
    <div class="modal-content">
      <div class="modal-header">
        <h5 class="modal-title" id="exampleModalLabel">Modal title</h5>
        <button
          type="button"
          class="btn-close"
          data-mdb-dismiss="modal"
          aria-label="Close"
        ></button>
      </div>
      <div class="modal-body">
      <!-- otro modal -->

        <!-- Button trigger modal -->
<button
  type="button"
  class="btn btn-primary"
  data-mdb-toggle="modal"
  data-mdb-target="#exampleModal2"
>
  Launch demo modal
</button>



      <!-- Fin otro modal -->
      </div>
      <div class="modal-footer">
        <button type="button" class="btn btn-secondary" data-mdb-dismiss="modal">
          Close
        </button>
        <button type="button" class="btn btn-primary">Save changes</button>
      </div>
    </div>
  </div>
</div>

<!-- Modal -->
<div
  class="modal fade mt-5"
  id="exampleModal2"
  tabindex="-1"
  aria-labelledby="exampleModalLabel2"
  aria-hidden="true"
>
  <div class="modal-dialog">
    <div class="modal-content">
      <div class="modal-header">
        <h5 class="modal-title" id="exampleModalLabel2">Modal title</h5>
        <button
          type="button"
          class="btn-close"
          data-mdb-dismiss="modal"
          aria-label="Close"
        ></button>
      </div>
      <div class="modal-body">...</div>
      <div class="modal-footer">
        <button type="button" class="btn btn-secondary" data-mdb-dismiss="modal">
          Close
        </button>
        <button type="button" class="btn btn-primary">Save changes</button>
      </div>
    </div>
  </div>
</div>

And this is how the modals are display: