what if someone sold you a Apple Watch but you don’t know there Apple ID or password

You either get the seller to unlock the watch or you return the watch to whoever you bought it from and get your money back. If you can't find them or they refuse, then you recycle the phone because an Activation Locked device can only be unlocked with the credential used to lock it. Apple will NOT help you. We cannot help you.

Get your money back. It will not work unless it is unlocked and activation lock removed.