Make featured image background image - html

Question

On my wordpress posts I want to add the post thumbnail at the top of the page to be full width. I want it to cover the full width of the page, and when the page gets bigger the image crops or zooms in.(similar to this https://www.inthefrow.com/2016/10/3-amazing-places-eat-mykonos.html) My code below is a work in process. It works in making the picture a background image, but it is not full width. It will only be the width of the picture. I would appreciate any help. Thanks in advance.
style.php
<?php
get_header();
if (have_posts()) :
while (have_posts()) : the_post(); ?>
<article class="post">
<?php $featuredImage = wp_get_attachment_url( get_post_thumbnail_id($post->ID), 'full' ); ?>
<div class="banner" style="background:url(<?php echo $featuredImage; ?>) no-repeat;"></div>
<?php wpb_set_post_views(get_the_ID()); ?>
<div class="post-info">
<h1 class="post-title"><?php the_title(); ?></h1>
<h2 class="post-date"><?php echo strip_tags(get_the_term_list( $post->ID, 'location', 'Location: ', ', ', ' • ' ));?><?php the_date('F m, Y'); ?></h2>
</div>
<div class="post-content"><?php the_content(); ?></div>
<div id="wrapper-footer"><div class="post-footer"><h1 class="post-footer-comment"><?php comments_popup_link ('No Comments', '1 Comment', '% Comments', 'post-footer-comment-count', 'none'); ?></h1><div class="share"><span>share</span> <?php get_template_part( 'share-buttons-post' ); ?></div></div>
<div class="post-footer-bloglovin"><h1>never miss a post</h1><h2>follow by email'</h2></div></div>
<?php get_template_part( 'prevandnextpost' ); ?>
<?php get_template_part( 'related-posts' ); ?>
<?php comments_template(); ?>
</article>
<?php endwhile;
else :
echo '<p>No content found</p>';
endif;
get_footer();
?>
css
.banner {
max-width: 100%;
width:100%;
height:700px;
background-size: cover;
background-position: center;
background-repeat: no-repeat;
background-attachment: fixed;
}

Answer 1

background-size: cover;
would do

Answer 2

Please ensure that wordpress is retrieving full width image path.
Post thumbnail should be full sized.
Check the same thorugh inspect element image url 'Open in new tab'.