I believe in God.
It's a faith-based belief...
...there's no "proof"...there's nothing to point to to say "See..I TOLD you He was real!"...there's nothing that I can hold or touch, or that you can ever objectively sense to demonstrate to another person that God is real.
Faith, in all of it's various forms and flavors, is a highly personal and highly subjective matter for anyone who has it, but none of us...Christian, Muslim, Hindu, Buddhist, Taoist, etc. can ever "prove" the existance of diety.
We simply accept that He/She/It exists, because of our faith.
Regarding atheism, my response to atheists is always the same...
If you are right and I'm wrong, and there is no God, no heaven, and no hell...then when I die, I'm just over...one minute conscious and living, the next minute dead and gone...the end, put a sock in it, it's been a great run, fini!
BUT...If it turns out I'm right and you're wrong...and there is another plane of existence beyond this pale realm, with God in control, and a real heaven, and a real hell...well now, by the time you're in a position to realize that, it's just a little too late for you isn't it
I'm just sayin....