Showing current category posts in “recent posts”-block

Hello @selectedbymila
For shows posts from the same category as the current post code is:

function wpb_postsbycategory() {
// the query
$term_list = get_the_terms(get_the_id(), 'category');
$the_query = new WP_Query( array( 
    'category_name' => $term_list[0]->name, 
    'posts_per_page' => 3 
) ); 
    
// The Loop
if ( $the_query->have_posts() ) {
    $string .= '<ul class="postsbycategory widget_recent_entries">';
    while ( $the_query->have_posts() ) {
        $the_query->the_post();
            if ( has_post_thumbnail() ) {
            $string .= '<li>';
            $string .= '<a href="' . get_the_permalink() .'" rel="bookmark">' . get_the_post_thumbnail($post_id, array( 50, 50) ) . get_the_title() .'</a></li>';
            } else { 
            // if no featured image is found
            $string .= '<li><a href="' . get_the_permalink() .'" rel="bookmark">' . get_the_title() .'</a></li>';
            }
            }
    } else {
    // no posts found
 $string .= '<li>No Posts Found</li>';
}
$string .= '</ul>';
    
return $string;
    
/* Restore original Post Data */
wp_reset_postdata();
}
// Add a shortcode
add_shortcode('categoryposts', 'wpb_postsbycategory');

Add this code in function.php and use shortcode in you template as normal [categoryposts] and if you want to use this in php file then use like this echo do_shortcode(‘[categoryposts ]’);