Where will you spend eternaty after you die?

This is a question i ask myself alot....I don't really know though i wonder if there's really a god or a satan. What i dont understand is if there is a god then why is the galaxy endless and this planet is supposedly the only 1 that has life on it? Why do black holes exist and how can you be sure there endless? Maybe they could lead into alternate universes with other lifeforms... Another theory i have is what if the christians "God" is really the bad person? Allow me to explain. There are religions out there that make satan to look the the good guy, i dont know the proper terms but they do exist. What if satan is really the good guy and the jewish religion is making god to look like the good 1? I'm not sure really thats just a theory of mine but if heaven is really a real place then i would want to go there.