Wordpress Page not loading correct with Stylepath - wordpress

Question

I have got an error in my code and I cant find why and where it orginates. But I know the template isnt loading correct. I believe the problem could start in the code below.
The problem started when I changed echo site_url to echo get_post_type_archive_link.
single-event.php
<?php
get_header();
while(have_posts()) {
the_post(); ?>
<div class="page-banner">
<div class="page-banner__bg-image" style="background-image: url(<?php echo get_theme_file_uri('/images/ocean.jpg') ?>)"></div>
<div class="page-banner__content container container--narrow">
<h1 class="page-banner__title"><?php the_title();?></h1>
<div class="page-banner__intro">
<p>DONT FORGETT TO REPLACE ME LATER!!</p>
</div>
</div>
</div>
<div class="container container--narrow page-section">
<div class="metabox metabox--position-up metabox--with-home-link">
<p>
<a class="metabox__blog-home-link" href="<?php echo site_url('/blog'); ?>">
<i class="fa fa-home" aria-hidden="true"></i> Events Home</a>
<span class="metabox__main"><?php the_title(); ?></span>
</p>
</div>
<div class="generic-content"><?php the_content();?></div>
<h2>
<?php }
get_footer();
?>
single.php
<?php
get_header();
while(have_posts()) {
the_post(); ?>
<div class="page-banner">
<div class="page-banner__bg-image" style="background-image: url(<?php echo get_theme_file_uri('/images/ocean.jpg') ?>)"></div>
<div class="page-banner__content container container--narrow">
<h1 class="page-banner__title"><?php the_title();?></h1>
<div class="page-banner__intro">
<p>DONT FORGETT TO REPLACE ME LATER!!</p>
</div>
</div>
</div>
<div class="container container--narrow page-section">
<div class="metabox metabox--position-up metabox--with-home-link">
<p>
<a class="metabox__blog-home-link" href="<?php echo get_post_type_archive_link('event'); ?>">
<i class="fa fa-home" aria-hidden="true"></i> Blog Home</a>
<span class="metabox__main">Posted by <?php the_author_posts_link(); ?> on <?php the_time('n.j.y'); ?> in <?php echo get_the_category_list(', '); ?></span>
</p>
</div>
<div class="generic-content"><?php the_content();?></div>
<h2>
<?php }
get_footer();
?>
Error message: