Missing Author Information

To display the author’s avatar within The Loop use get_avatar() like that:

<?php print get_avatar(get_the_author_meta('ID'), '30', '', '', ['class' => 'foo-bar']); ?>

To display the author’s display name within The Loop use the_author():

<?php the_author(); ?>

---

So put everything inside The Loop and then:

<?php
while (have_posts()) : the_post();
  ?>

  <div class="row">
    <div>
      <h1 class="primary-color">
        <?php the_title(); ?>
      </h1>
      <span class="avatar">
        <?php print get_avatar(get_the_author_meta('ID'), '30', '', '', ['class' => 'foo-bar']); ?>
      </span>
      by <span class="primary-color"><?php the_author(); ?></span>
      <span class="pipe">|</span>
      <span class="date"><?php echo get_the_date(); ?></span>
    </div>
  </div>

  <div class="row">
    <?php the_content(); ?>
  </div>

<?php endwhile; ?>