I send my xbox to the repair center in germany using my local post office instead of ups

If you have requested UPS since they have an affiliation with them, I think it would be a problem.

Yes they charged me and thanks to you

They didn't scan the label but they wrote the adress the xbox should be delivered to, and taped their label near the ups label, after I contacted them they said that the shipment cant be cancelled and they said also that there is no need to worry and the
shipment will get there in three days

It may cause an issue since it's a ups label. Did your local post office scan the label? If they did and gave you a receipt for it you should be able to track it with a tracking number on the receipt. I would contact them immediately about this though.

Did the post office charge you when they took the package or did you put it in a drop box? If you put it in a drop box, I would recommend contacting the post office (in person) to see how the package will be handled. If your return address is on the label,
they may return the package to you, but you should make them aware of the situation. With proper identification, they may return the package to you so you can take it to UPS.

Best wishes,

Cowgirl