Back to category by post ID

<?php
		$category = get_the_category();
		$cat_nm = $category[0]->cat_name;
	if (is_single() && in_category( $cat_nm )) {
		$category_id = get_cat_ID( $cat_nm );
		$category_link = get_category_link( $category_id );
		?>
	<a href="<?php echo esc_url( $category_link ); ?>">Back to all <?php echo $cat_nm; ?></a>
<?php } else {} ?>