File upload using wordpress custom plugin

I’m trying to upload files to the default “wp-content/uploads” directory. Have tried almost all the available tags, still not working. You can follow this steps:

//taking image in $name_icon
$name_icon = $_POST['myfile'];
    
    // WordPress environment
                    require( dirname(__FILE__) . '/../../../wp-load.php' );
                     
                    $wordpress_upload_dir = wp_upload_dir();
             
                    $i = 1; // number of tries when the file with the same name is already exists
                     
                    $profilepicture = $_FILES['myfile'];
                    $new_file_path = $wordpress_upload_dir['path'] . '/' . $profilepicture['name'];
                    $new_file_mime = mime_content_type( $profilepicture['tmp_name'] );
                     
                    if( empty( $profilepicture ) )
                        die();
                     
                    if( $profilepicture['error'] )
                        die( $profilepicture['error'] );
                     
                    if( $profilepicture['size'] > wp_max_upload_size() )
                        die( 'It is too large than expected.' );
                     
                    if( !in_array( $new_file_mime, get_allowed_mime_types() ) )
                        die( 'WordPress doesn\'t allow this type of uploads.' );
                     
                    while( file_exists( $new_file_path ) ) {
                        $i++;
                        $new_file_path = $wordpress_upload_dir['path'] . '/' . $i . '_' . $profilepicture['name'];
                    }
                     
                    // looks like everything is OK
                    if( move_uploaded_file( $profilepicture['tmp_name'], $new_file_path ) ) {
                     
                        $upload_id = wp_insert_attachment( array(
                            'guid'           => $new_file_path, 
                            'post_mime_type' => $new_file_mime,
                            'post_title'     => preg_replace( '/\.[^.]+$/', '', $profilepicture['name'] ),
                            'post_content'   => '',
                            'post_status'    => 'inherit'
                        ), $new_file_path );
                     
                        // wp_generate_attachment_metadata() won't work if you do not include this file
                        require_once( ABSPATH . 'wp-admin/includes/image.php' );
                     
                        // Generate and save the attachment metas into the database
                        wp_update_attachment_metadata( $upload_id, wp_generate_attachment_metadata( $upload_id, $new_file_path ) );