How to direct user after comment save

Use the filter comment_post_redirect:

add_filter( 'comment_post_redirect', 'comment_redirect' );

function comment_redirect( $location ) {
    $location = 'http://example.com/sample-page';
    // or:
    // $location = get_page_link( page_ID );
    // $location = get_page_link( get_page_by_path( 'sample-page' )->ID )
    return $location;
}