Just an idea.
Would it be possible to send the information I got from barcode and send it to the dhl homepage for shipment tracking?
On the receipt they give me at the post office there is unfortunately no barcode on it only the shipment number. But the postal clerk usually puts a barcode sticker on the packet. So one could ask to take a quick shot with the barcode app then save the number and track the shipment later on the dhl page.