Well I just sold a neck for not much but I didn't know that many papers and things that I had to sign so I'm just asking is all those thing that I had to sign is like part of the normal selling ?
It was my first time by the way

You sold a neck? Do you mean a necklace?

Not sure what is "normal", but I assume whoever you sold it to was trying to make sure it wasn't stolen. It seems a good precaution to take - especially if it was an expensive item.

It depends on what you were asked to sign. Hopefully you have read all the stuff carefully before agreeing. The agreement usually includes information about taxes, theft, damages etc.