Very disappointed by their procedure not at all or...

Very disappointed by their procedure not at all oriented on the comfort of the client. You order a product that appears in the supplier's stock (online stock), you wait 7 days of common sense (because you are told that it takes 3-5 working days), you give an email to ask what is happening, after which you receive an answer like "ok, we'll contact the supplier". And of course the next day they told me that the product was not actually in stock. After I canceled the order, I received my money only after 4 days. For such cases, an effort can be made to speed up the return of the money.

Didn't you have to contact the supplier right away? If your site is not able to automatically subtract -1 from the number of pieces available (how it works on PcGarage / eMag), then get personally involved to make sure that no such situations can happen.