Hi,
The language of the order status email sent to the customer is sent in the language of the customer.
The language of the payment notification email sent to the administrator is also sent in the language of the customer.
If you want to force the language of that last email, you would have to change the line:
$notify_url = HIKASHOP_LIVE.'index.php?option=com_hikashop&ctrl=checkout&task=notify¬if_payment='.$this->name.'&tmpl=component&lang='.$this->locale . $this->url_itemid;
to:
$notify_url = HIKASHOP_LIVE.'index.php?option=com_hikashop&ctrl=checkout&task=notify¬if_payment='.$this->name.'&tmpl=component&lang=xx' . $this->url_itemid;
where xx is the 2 letters code of the language you want in the file plugins/hikashoppayment/paypal/paypal.php