What is beyond our universe?
Well, our universe is everything within the radius of the matter and energy that is expanding since the big bang. We can calculate the size of the universe, but we have problems seeing stuff that is very very far away, for obvious reasons. Our technology is currently to weak to see if there is anything outside our universe. As of now, there just seems to be emptyness. Maybe there are more universes, maybe not, we don't know yet.
What happens after you die?
The scientific part is this: your current "you", your personality, character and self-wareness, are the results of any information your brain acquired, stored, and how it processed it. Which means that everything you are is basically in your brain, in form of physical matter. When you die, your brain decomposes, and thus also the matter that makes you you. The logical result is, that then there is nothing, same as before you were born.
Some people believe that there is some other form of existence after you die. I personally have my doubts for various reasons. Like, to start, that there is no theory how that should work. If your brain is gone, so is everything that makes you you. Even if some part of yourself would continue to exist, it wouldn't matter much, since it would be a new persona of sorts. In addition, without a brain or sense or anything, how would you perceive anything? In short, to me, and to science, the most logical thing is that there is just nothing. Which has it's ups and downs. Downside is, that everything is over for good. The upside is: if there'd be something after death, it could be good or it could be bad. So "nothing" is better than bad already. What's interesting though is this: while you are dead, obviously, time does not pass for you. So, if for some reason, in a million years, humanity would still exist and would have progressed in matters of technology, they might build a device that could resurrect you. Or maybe in 10 million years. Who knows. If that would happen, and future humanity would resurrect you, then for you it would happen the instant you die, since, again, time doesn't pass for you when you are dead.
Of course there are many problems with this. Maybe they'd do that to torture you, or maybe they couldn't reconstruct your whole brain, so your personality would be gone again, in which case you wouldn't have gained anything. But, you will find that out the moment you die. It's quite unlikely though. That's why some people freeze their bodies or brains, to stop the decomposition. Currently, there is no way to freeze a body that way without harming it. But the people who do that hope, that many years in future, there might be a technology that enables the future humans to unfreeze and resurrect those who die in our present. Whether that will ever work out or not, nobody knows. But they got a better chance than people who let their body rot.
Is god real? Is the devil real?
That's a matter of faith, a personal opinion. For me, neither god nor the devil are real. For many many many reasons. There is a 0% chance for them to be real, for me. I can't believe in them. I'm 100% atheist. Explaining here why would probably be too much.