<div class="accordion" id="accordionExample">

  <div class="accordion-item">

    <h2 class="accordion-header" id="headingOne">

      <button

        class="accordion-button"

        type="button"

        data-mdb-toggle="collapse"

        data-mdb-target="#collapseOne"

        aria-expanded="true"

        aria-controls="collapseOne"

      >

        Accordion Item #1

      </button>

    </h2>

    <div id="collapseOne" class="accordion-collapse collapse show" aria-labelledby="headingOne" data-mdb-parent="#accordionExample">

      <div class="accordion-body">

        <div class="form-outline test mb-2">

          <input type="text" id="form12" class="form-control" value="1233"/>

          <label class="form-label" for="form12">Example label</label>

        </div>

        <div class="mb-2 test">

          <select class="select" name="test1" id="1">

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

          </select>

          <label class="form-label select-label">Größe</label>

        </div>

      </div>

    </div>

  </div>

  <div class="accordion-item">

    <h2 class="accordion-header" id="headingTwo">

      <button

        class="accordion-button collapsed"

        type="button"

        data-mdb-toggle="collapse"

        data-mdb-target="#collapseTwo"

        aria-expanded="false"

        aria-controls="collapseTwo"

      >

        Accordion Item #2

      </button>

    </h2>

    <div id="collapseTwo" class="accordion-collapse collapse" aria-labelledby="headingTwo" data-mdb-parent="#accordionExample">

      <div class="accordion-body">

        <div class="form-outline test mb-2">

          <input type="text" id="form12" class="form-control" value="1233"/>

          <label class="form-label" for="form12">Example label</label>

        </div>

        <div class="mb-2">

          <select class="select test" name="test1" id="1">

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

          </select>

          <label class="form-label select-label">Größe</label>

        </div>

      </div>

    </div>

  </div>

  <div class="accordion-item">

    <h2 class="accordion-header" id="headingThree">

      <button

        class="accordion-button collapsed"

        type="button"

        data-mdb-toggle="collapse"

        data-mdb-target="#collapseThree"

        aria-expanded="false"

        aria-controls="collapseThree"

      >

        Accordion Item #3

      </button>

    </h2>

    <div id="collapseThree" class="accordion-collapse collapse" aria-labelledby="headingThree" data-mdb-parent="#accordionExample">

      <div class="accordion-body">

        <div class="form-outline test mb-2">

          <input type="text" id="form12" class="form-control" value="1233"/>

          <label class="form-label" for="form12">Example label</label>

        </div>

        <div class="mb-2 test">

          <select class="select" name="test1" id="1">

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

            <option value="1" data-mdb-secondary-text="<Test 123">Option</option>

          </select>

          <label class="form-label select-label">Größe</label>

        </div>

      </div>

    </div>

  </div>

</div>

​