Pls Help Me To Create This Widget

i need show my last news on special category

<?php
    $my_query = new WP_Query('showposts='. dynamic_sidebar( 'lastnews' ) .'&cat=1');
    $active = NULL;
    while ($my_query->have_posts()):
        $my_query->the_post();
        $thumbnail_id = get_post_thumbnail_id();
        $thumbnail_url = wp_get_attachment_image_src( $thumbnail_id, 'thumbnail-size', true );
        $do_not_duplicate = $post->ID;
        if( $active == NULL ){ $active = "active"; }else{ $active = deactive ; }
            ?>
                <div class="item <?php echo $active; ?>">
                    <img src="<?php echo $thumbnail_url[0]; ?>" alt="<?php the_title(); ?>">
                    <div class="carousel-caption transition">
                        <h3 class="text-white"><?php the_title(); ?></h3>
                        <div class="text-center">
                            <p><?php the_excerpt(); ?></p>
                            <a class="btn btn-danger" href="<?php the_permalink() ?>"  target="_blank" > <span class="glyphicon glyphicon-sunglasses"></span> مشاهده </a>
                        </div>
                    </div>
            </div>

<?php endwhile; ?>

But dynamic_sidebar( 'lastnews-right' ) Dosent Work on lane 2. I Create Widget With This Style.

function create_lastnews( $name, $id, $description ) {

register_sidebar(array(
    'name' => __( $name ),
    'id' => $id,
    'description' => __( $description ),
    'before_widget' => '',
    'after_widget' => '',
    'before_title' => '',
    'after_title' => ''
));
}

create_lastnews( 'Last News Category', 'lastnews', 'Enter Id Of Your Category To Show News' );

Pls Help Me I Can Make This News With An Other Work ?