If God, Jesus, the devil, angels, and demons were all real, we still couldn’t rely on the Christian Bible as gospal (pun intended) — it was written by humans, specifically men, who could have misunderstood or invented things. Think of it like the Snyderverse in Man of Steel: Superman is portrayed as a brooding, violent character — but that’s not his true nature. In Batman v Superman, Batman is straight-up killing people — also not his normal characterization.
So even if much of the Bible reflects real events or real beings, parts of it could still be distorted, exaggerated, or entirely made up by the people who wrote it down.
And then the popes edited it further.
That’s completely and historically not true. Popes as we know them generally came about centuries later, by that time the New Testament was already in wide circulation (it was being widely circulated in three continents by the beginning of the second century so editing it after that point would have been impossible)