I know God exists, I don't believe he exists, i really know. If it's possible for me to find out, it's possible for everyone.
If God is real, why doesn't he reveal himself? He does, he really does. But for one it's quite cool he doesn't rub his greatness in our face, because we would only be depressed that we could never gain what he has and never be who he is. And that wouldn't be love if God did it to depress us. And besides, God is God, it doesn't mather what men do or say, it doesn't change the truth, he doesn't need men to become who he is, because he already is who he is.
It's also cool to find out about God and getting to know him when you search for it yourself, out of your own will.
You might resemble it with a very rich man who doesn't talk to anyone about his forture, because he only wants to be surrounded by true friends and share it with them.
The great thing is this way of life won't keep going on like this forever. Everyone will have had the same time and choices in different ways and everyone is waiting for the time when everyone will be raised from the dead to be judged for their deeds. From those who've been given more, more will be expected. And it's still possible to get rid of evil deeds you did or someone else did through Jesus. Not to be free of punishment to keep doing evil deeds. But to be free of doing evil.
I'm not entirely sure about what exactly happens when someone dies, but I suppose we'll all find that out

But I do know some things that will happen. You'll just have to find out that God is trustworthy and only speaks the truth. If God lies he would be judged by his own law, it's even logical.
So, do I know what's in the afterlife out of my own intelligence? No, I haven't been there. How do I know anything about the afterlife? I know God exists and speaks the truth and I know things He said about things to come. All I have to do is sit back, relax, and wait for those things to come.