All invented by Nick

Nick clearly makes up much of what he tells us in his narrative. FSF intends us to think that Nick does this quite naturally and without malice. For example he invents all the stuff around Gatsby and Daisy's romance 5 years ago. So why do we believe anything else? Jordan in this sense is a manufactured character to give credence to histories Nick couldn't have known about. The more I read the novel the less I believe in it!