Unable to reset post data in wordpress custom query

After reading the documentation for multiple loops in one page here, I only had one WP_Query for both the loops. I stored the ID’s of all the posts from the desired category and check for them in the second loop and continue over them. Here’s the final code –

first loop

        <?php
        $args = array(
            'post_type' => 'post',
            'post_status' => 'any',
            'category' => 3,
            'posts_per_page' => 4);
        $query_var = new WP_Query($args);
        if ($query_var->have_posts()):
        while ($query_var->have_posts()):
            $query_var->the_post();
            $do_not_duplicate[] = $post->ID; ?>
            <div class="patta p-4 col-lg-3 col-md-6">
                <!-- FIX THIS -->
                <img class="card-img-top"
                     src="https://wordpress.stackexchange.com/questions/323799/<?php the_post_thumbnail(); ?>"
                     alt="<?php the_post_thumbnail_caption() ?>"/>
                <h4><b><?php the_title(); ?></b><br></h4>
                <p>
                    <a href="#">Link</a>
                </p>
            </div>
        <?php endwhile; ?>

Second Loop

if (have_posts()):
                while (have_posts()):
                    the_post();
                    if (in_array($post->ID, $do_not_duplicate)) continue;
                    ?>
                    <div class="patta p-4 col-lg-3 col-md-6">
                        <!-- FIX THIS -->
                        <img class="card-img-top"
                             src="https://wordpress.stackexchange.com/questions/323799/<?php the_post_thumbnail(); ?>"
                             alt="<?php the_post_thumbnail_caption() ?>"/>
                        <h4><b><?php the_title(); ?></b><br></h4>
                        <p>
                            <a href="#">Link</a>
                        </p>
                    </div>
                <?php
                endwhile;
                endif;
            endif;
            ?>