woocommerce add receipt of invoice to checkout, with validation and display it in wp-admin

woocommerce paragon lub faktura

add_filter( 'woocommerce_checkout_fields' , 'custom_override_checkout_fields' );

// ADD NIP AND REARRANGE
function custom_override_checkout_fields( $fields ) {
     $fields['billing']['pk_nip'] = array(
        'label'     => __('NIP', 'woocommerce'),
    'placeholder'   => _x('Wpisz NIP, jeżeli chcesz otrzymać fakturę', 'placeholder', 'woocommerce'),
    'required'  => false,
    'class'     => array('form-row-wide'),
    'clear'     => true,
    'priority'  =>35, //this way you can change order of fields in checkout
     );
     $fields['billing']['pk_invoice_receipt'] = array(
      'label'     => __('Faktura VAT lub paragon', 'woocommerce'),
      'type'      => 'radio',
      
      'required'  => true,
      'class'     => array('form-row-wide'),
      'clear'     => true,
      'priority'  =>5,
      'options'         => array(
        'paragon'         => 'Paragon',
        'faktura'    => 'Faktura',
      ),
   );
     return $fields;
}

add_action( 'woocommerce_admin_order_data_after_shipping_address', 'my_custom_checkout_field_display_admin_order_meta', 10, 1 );
add_action( 'woocommerce_checkout_update_order_meta', 'pk_save_faktura_paragon' );
function pk_save_faktura_paragon( $order_id ){
 
	if( !empty( $_POST['pk_invoice_receipt'] ) )
		update_post_meta( $order_id, 'pk_invoice_receipt', sanitize_text_field( $_POST['pk_invoice_receipt'] ) );
 
 
	if( !empty( $_POST['pk_nip'] )  )
	update_post_meta( $order_id, 'pk_nip', sanitize_text_field( $_POST['pk_nip'] ) );
 
}
function my_custom_checkout_field_display_admin_order_meta($order){
   
    echo '<p><strong>'.__('FAKTURA LUB PARAGON').':</strong> ' . get_post_meta( $order->get_id(), 'pk_invoice_receipt', true ) . '</p>';
    echo '<p><strong>'.__('NIP').':</strong> ' . get_post_meta( $order->get_id(), 'pk_nip', true ) . '</p>';
}

add_action( 'woocommerce_after_checkout_validation', 'pk_validate_invoice', 10, 2);
 
function pk_validate_invoice( $fields, $errors ){
 
    if ( $fields[ 'pk_invoice_receipt' ]==="faktura"&&(empty($fields[ 'pk_nip' ])||empty($fields[ 'billing_company' ]))   ){
        $errors->add( 'validation', 'Jeżeli chcesz otrzymać Fakturę, uzupełnij nazwę firmy oraz NIP' );
    }
}