Django template forloop counter change design after x article

Hi!
You've got an error in markup
the first div after {% if forloop.first %} is closing after {% endif %}. You should put openning div outside of forloop or make in every if-branch. (I prefer the second way)
so, you can try this:

<div class="trending position-relative pb-65">
    <div class="container">
        <div class="row">
            {% for article in healtharticles %}

            <div class="col-lg-4 col-md-12 mb-4 mb-lg-0">
                <!-- News block -->
                {% if forloop.first %}
                <div>

                    <!-- Featured image -->
                    <div class="bg-image hover-overlay shadow-1-strong ripple rounded-5 mb-4"
                        data-mdb-ripple-color="light">
                        <img src="https://mdbootstrap.com/img/new/fluid/city/113.jpg" class="img-fluid" />
                        <a href="#!">
                            <div class="mask" style="background-color: rgba(251, 251, 251, 0.15);"></div>
                        </a>
                    </div>

                    <!-- Article data -->
                    <div class="row mb-3">
                        <div class="col-6">
                            <a href="" class="text-info">
                                <i class="fas fa-plane"></i>
                                Travels
                            </a>
                        </div>

                        <div class="col-6 text-end">
                            <u> 15.07.2020</u>
                        </div>
                    </div>

                    <!-- Article title and description -->
                    <a href="" class="text-dark">
                        <h5>This is title of the news</h5>

                        <p>
                            Lorem ipsum dolor sit amet consectetur adipisicing elit. Odit, iste aliquid. Sed
                            id nihil magni, sint vero provident esse numquam perferendis ducimus dicta
                            adipisci iusto nam temporibus modi animi laboriosam?
                        </p>
                    </a>
                </div>

                {% else %}
                <hr />
                <div>

                    <!-- News -->
                    <a href="" class="text-dark">
                        <div class="row mb-4 border-bottom pb-2">
                            <div class="col-3">
                                <img src="https://mdbootstrap.com/img/new/standard/city/041.jpg"
                                    class="img-fluid shadow-1-strong rounded" alt="" />
                            </div>

                            <div class="col-9">
                                <p class="mb-2"><strong>Lorem ipsum dolor sit amet</strong></p>
                                <p>
                                    <u> 15.07.2020</u>
                                </p>
                            </div>
                        </div>
                    </a>
                </div>
                {% endif %}
                <!-- News block -->
            </div>
            {% endfor %}
        </div>
    </div>
</div>