PHP code for automatically change WooCommerce order status

I would like to change the status of every new WooCommerce order depending on a custom field (shopart) with PHP.

I already tried to write a function in the functions.php file but I failed.

// set Custom Order Status at WooCommerce Checkout Process
 
add_action( 'woocommerce_thankyou', 'uebes_thankyou_change_order_status' );
 
function uebes_thankyou_change_order_status( $order_id ){
   if( ! $order_id ) return;{
      $order = wc_get_order( $order_id );
      // update order status dependimg to custom field shopart 
      if(get_post_meta($order->id,'shopart',true) == 'Shop Vorbestellungen'){
        $order->update_status( 'vorbestellung' );
      }else{
        $order->update_status( 'bestellung-neu' );  
      }
   }
}

Answer

// set Custom Order Status at WooCommerce Checkout Process

add_action('woocommerce_thankyou', 'uebes_thankyou_change_order_status', 10, 1);

function uebes_thankyou_change_order_status($order_id) {

    if (!$order_id)
        return;

    //create an order instance
    $order = wc_get_order($order_id);
    // update order status dependimg to custom field shopart 
    if (get_post_meta($order_id, 'shopart', true) == 'Shop Vorbestellungen') {
        $order->update_status('vorbestellung');
    } else {
        $order->update_status('bestellung-neu');
    }
}