List posts that are in the same category as the current post title

First you need to fetch the current category, then grab posts. So, try

<ul>
<?php
global $post;
$category = get_the_category($post->ID);

$args = array( 'numberposts' => -1, 'offset'=> 1, 'category' => $category );
$myposts = get_posts( $args );
foreach( $myposts as $post ) : setup_postdata($post); ?>
    <li><a href="https://wordpress.stackexchange.com/questions/56247/<?php the_permalink(); ?>"><?php the_title(); ?></a></li>
<?php endforeach; ?>
</ul>