add_filter('angelleye_paypal_plus_shipping_line1', 'th_angelleye_paypal_plus_shipping_line1', 10, 2);

    function th_angelleye_paypal_plus_shipping_line1($shipping_address_1, $order_id) {
        $shipping_address = get_post_meta($order_id, '_shipping_address_1', true);
        if (empty($shipping_address)) {
            $house_no = get_post_meta($order_id, '_billing_hausnummer', true);
            if (empty($house_no)) {
                $house_no = get_post_meta($order_id, 'billing_hausnummer', true);
            }
        } else {
            $house_no = get_post_meta($order_id, '_shipping_haus_nummer', true);
            if (empty($house_no)) {
                $house_no = get_post_meta($order_id, 'shipping_haus_nummer', true);
            }
        }
        if (!empty($house_no)) {
            $shipping_address_1 = $shipping_address_1 . ' ' . $house_no;
        }
        return $shipping_address_1;
    }