Things are less confusing once you realize that Christianity has nothing new or unique about it. The bible is obviously a compilation of myths and legends from a variety of cultures, with some fairly universal themes and figures. The interpretations of the stories change depending on current events--that's why you, Jst are certain that you see biblical truth when you look around at the world. Muslims say the same thing about the Quran.People always see their myths reflected in the real world.
That's the point of these stories; before the scientific method gave us a systematic way to figure out what was going on, these old stories were the main way to teach how the world worked. These stories are important and interesting and fun, that's why they keep getting retold: Star Wars, Batman, Harry Potter, Twilight and The Avengers. But just like these modern popular versions, they are not factual!
Pre-Christian pagan belief systems do not have a devil or super-evil villain god. The "angel of death" was in charge of the underworld or the next world or whatever happened after people died. He was not a bad guy; that was just his job description, like Shiva for Hindus, or Hades for the ancient Greeks.
The devil figure with the horns, tail and cloven hooves was designed after the ancient god Pan, who ruled over chaos (pan=panic, pandemonium). People today often think more of Lord Voldemort, Darth Vader, the Grim Reaper or the Mad Scientist being up to no good.
The "good god of light" versus "evil demon of darkness" came into Christianity through Persian Zoroastrianism, IIRC.
The gods were like extra-powerful people, kinda like superheroes, with good and bad qualities. Some gods (Thor, Krishna) embodied nobler qualities like courage and selflessness. Other gods (Eshu, Mercury, Raven, Coyote) existed to trick people, to teach a lesson or to make people think.
Gods like Babaluaye, Loki, Shango and Bacchus messed things up, forgot things, threw tantrums and destroyed stuff. Some, like Zeus, had sex with humans or animals, or messed around with dark powers, creating demi-gods (Jesus, Hercules, Hulk) and other magical creatures (elves, fairies). Gods were not only puny, but sometimes naughty!
A particular god might set up silly tests for humans or challenge another god to a contest. If bad stuff happened, it could be because a certain god had a bad day, was jealous of another god, did not like the sacrifices, or was not being worshipped enough. (Funny how much that sounds like the OT Yahweh.)
The NT tried to go all monotheistic, and smooshed the ancient gods together into one big god. He was supposed to be this good, smart, loving grand-dad, like a calmer, less sexual version of the horny old goat Zeus. Pagans added in the son figure from young, pretty-boy gods like Apollo.
(I can't remember where the holy spirit part of the Trinity came from off the top of my head. Haven't taught this in a while...)
The naughty, chaotic, destructive and sexy characteristics didn't fit with the good grandpa persona, so those aspects were combined into the persona of Satan, the evil one. When bad stuff happens, he became the scapegoat so you don't blame the big good guy. He was also given rule over death and the underworld, since the good guy couldn't be expected to do that.
So, you need to know about how similar the bible stuff is to every other culture's mythology. Then you might be able to understand why so many people here can't take you seriously when you try to argue that your religious stuff (unlike everyone else's) is factually true. And why there is no evidence for any culture's mythology being factually true.