Oh relax. Understand this simple thing: You cannot prove that your god exists but worship him through faith. Faith which only you can see and understand. The rest is made up assumptions.
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Some numbers:
(1) Christianity: About 2.3 billion followers.
(2) Islam: About 1.5 billion followers.
(3) Judaism: About 14 million followers.
Looks like just shy of 4 billion people have this faith you speak of.
How do you know another's faith.... it's a personal thing. Faith is your own thoughts and beliefs.
Yes you can share a similar faith with others, which are shown by the numbers above, but your own faith is personal to you.
Hence my comments above....