There’s no reason to doubt their authenticity. FootballLeaks have been bang on the money about everything they’ve leaked, and the fact that Ronaldo’s lawyers didn’t sue the feck out of Der Spiegel for publishing them speaks volumes.
It was dismissed because the evidence was obtained illegally. That doesn’t mean he didn’t do it. His lawyers repeatedly threatened to sue for publishing false evidence. Funnily enough they never went through with it.