Wrong device delivered - supplier is ignoring it by remaining silent

Does the seller have a proper imprint with an address in Germany? How long has it been? (Just a few facts, please ...)

I would announce the return by registered mail with a postal receipt and request the forwarding of the correct device within a 14-day period (so, demand it). If nothing happens after the deadline, try the same with a letterhead from a lawyer (maybe you know someone ..., otherwise pay for it).

What is the amount in dispute?

In parallel: use review portals. That sometimes helps ;-).

After the deadline, I would withdraw from the contract and reverse the payment. Then he will come to pick it up.

Another feedback from me on this topic... I had paid with Paypal... and with PP there is the so-called buyer protection. This applies 150 days from the payment date. It’s a bit complicated and you have to be meticulous with deadlines once you have initiated the process! First, another attempt at mediation is made. During this attempt, I properly returned the wrong device unused. Unfortunately, the seller still did not want to refund. Now Paypal has intervened and transferred the money back to me. I call that top! I surely wouldn’t have achieved that alone! :) Best regards, Steffi.

Strong! PayPal is therefore not the lawyer's favorite :)

Considering the fees Paypal charges for each payment, that is completely fine. With a decent credit card, it works the same way.

And it does not mean that the matter is over...