Hello my name is Nico and i have a lot of experience selling on Amazon, eBay and on Wallapop too. I used to sell my old things on eBay and i made a lot of money doing that (I made more o less 7800$). The only thing that you have to know is which is the best way to sell your product. I think, that I can help you a lot seling your products and improving your score on Amazon.
Thank you for your time
Nicolás Olabarría