Hi,
Under Appearance > Elements, you should be able to see a Hook Element named Single Post Entry Header.
Once you open it, you’ll see a bunch of codes.
Replace those codes with this one below:
<div id="custom-post-entry-header" class="custom-post-header grid-container">
<?php
global $post;
$author_id = $post->post_author;
?>
<div class="gravatar">
<?php echo get_avatar( $author_id ); ?>
</div>
<span class="author-name" itemprop="name">
<a href="<?php echo esc_url( get_author_posts_url( get_the_author_meta( 'ID' ) ) ); ?>">
<?php echo get_the_author_meta('display_name',$author_id ); ?>
</a>
</span>
<?php
the_title( '<h1 class="entry-title" itemprop="headline">', '</h1>' );
if ( has_excerpt() ) : // Only show custom excerpts not autoexcerpts ?>
<p class="entry-subtitle"><?php echo get_the_excerpt(); ?></p>
<?php endif; ?>
<time class="entry-date published" datetime="<?php echo esc_attr( get_the_date( 'c' ) ); ?>" itemprop="datePublished"><?php echo esc_html( get_the_date() ); ?></time>
</div>