How do we know the gospel speaks truth? How do we know that the one(s) who wrote the Bible, did write down the exact words that Jesus spoke? How do we know that if Jesus indeed spoke those words he wasn't the devil in disguise?
If the answer is that we just must believe, then this (the gospel, Jesus, the bible) would also form the perfect vessel for the devil, wouldn't it?
And how are the credulous, the believers, to discern beyween a true gospel, if such one exists, and a false one, whether simply made-up by men or positioned by the devil?

Does Jesus have answers for these questions too?

Because, frankly, "because god said" , to me sounds exactly what the devil would say to lead the credulous astray.