Legal advice on jewelry sales

Questioner

I delivered some jewelry to a gold buyer last night, my jewelry was titanium with gold, the girl behind the counter called her boss to ask if she could accept it, no problem for him, I get the amount of 520 euros but had to make a copy of my ID, I didn't have it with me at the time, I brought it this morning with more of the same kind of jewelry, she called her boss again, boss called the wholesaler, titanium is worthless, only gold, now they want me to pick up the jewelry again and bring the money back, I also received a receipt with the amount that was paid to me, what can I do with this, should I bring it back or is it like that, they are making a mistake, I don't have to respond anymore.

Lawyer

In principle, the buyer can no longer undo the purchase agreement. I don't think an appeal by him to error will succeed quickly, because the buyer is a professional and should know better. I advise you not to take any action and to keep the receipt.