For retrieving the post categories & post tags , we can use get_the_category and get_the_tags functions in wordpress. Here is the code snippet for both functions.

get_the_category() example:

<?php
    $categories = get_the_category();
	if ( ! empty( $categories ) ) {
	echo '<a href="' . esc_url( get_category_link( $categories[0]->term_id ) ) . '">' . esc_html( $categories[0]->name ) . '</a>';
};

?>

get_the_tags() example:

<?php
     $post_tags = get_the_tags();

     if ( $post_tags ) {
	foreach( $post_tags as $tag ) {
    echo $tag->name . ', '; 
     }
}
?>