Try changing it to this:
<div class="author-box">
<div class="avatar">
<?php echo get_avatar( get_the_author_meta( 'ID' ) ); ?>
</div>
<div class="author-info">
<h5 class="author-title"><?php printf( esc_attr__( 'About %s', 'the author' ), get_the_author_meta( 'display_name') );?></h5>
<div class="author-summary">
<p class="author-description"><?php echo wp_kses( get_the_author_meta( 'description' ), null ); ?></p>
</div>
</div>
</div>
Then change your CSS to this:
.author-box {
padding: 4%;
margin-top: 60px;
font-size: 1em;
display: -webkit-box;
display: -ms-flexbox;
display: flex;
}