please modified yoy loop to display single post which you have coded in single.php file
<?php
// Start the loop.
while ( have_posts() ) : the_post();
/*
* Include the post format-specific template for the content. If you want to
* use this in a child theme, then include a file called called content-___.php
* (where ___ is the post format) and that will be used instead.
*/
get_template_part( 'content', get_post_format() );
// If comments are open or we have at least one comment, load up the comment template.
if ( comments_open() || get_comments_number() ) :
comments_template();
endif;
// Previous/next post navigation.
the_post_navigation( array(
'next_text' => '<span class="meta-nav" aria-hidden="true">' . __( 'Next', 'twentyfifteen' ) . '</span> ' .
'<span class="screen-reader-text">' . __( 'Next post:', 'twentyfifteen' ) . '</span> ' .
'<span class="post-title">%title</span>',
'prev_text' => '<span class="meta-nav" aria-hidden="true">' . __( 'Previous', 'twentyfifteen' ) . '</span> ' .
'<span class="screen-reader-text">' . __( 'Previous post:', 'twentyfifteen' ) . '</span> ' .
'<span class="post-title">%title</span>',
) );
// End the loop.
endwhile;
?>