How to fix a Permalink that is not working in WordPress theme

Question

I have a WordPress "tube" theme. When I click on a thumbnail, it opens a new page which is my homepage. (It is supposed to take me to the post page) but I can type in the post page address to go there manually? How can I fix this in code. Here's a piece of code in image.php. i know some PHP but not very fluent so i can't quite connect the dots.

<header class="entry-header">
                <?php the_title( '<h1 class="entry-title">', '</h1>' ); ?>

                <div class="entry-meta">

                    <span class="entry-date"><time class="entry-date" datetime="<?php echo esc_attr( get_the_date( 'c' ) ); ?>"><?php echo esc_html( get_the_date() ); ?></time></span>

                    <span class="full-size-link"><a href="<?php echo esc_url( wp_get_attachment_url() ); ?>"><?php echo esc_html( $metadata['width'] ); ?> &times; <?php echo esc_html( $metadata['height'] ); ?></a></span>

                    <span class="parent-post-link"><a href="<?php echo esc_url( get_permalink( $post->post_parent ) ); ?>" rel="gallery"><?php echo get_the_title( $post->post_parent ); ?></a></span>
                    <?php edit_post_link( __( 'Edit', 'twentyfourteen' ), '<span class="edit-link">', '</span>' ); ?>
                </div><!-- .entry-meta -->
            </header><!-- .entry-header -->

Answer 1

You need to link to the actual post link.

maybe try to replace

post->post_parent 

with:

post->ID