The export of goods has to be confirmed at the last customs office in the EU. There is also a German Customs Office at Basel railway station. German Customs is not involved in the actual refund of the money. This is either be done by the seller directly or by a service company like Global Refund. You’ll have to contact them in order to find out whether you can get the money there (I doubt it, be the way).
I hope my answer is sufficient.