When most people look at the world around them, they see only the trees; they do not see the forest that is there. It should be obvious that God exists because of His creation, not only us humans, but the world we live in, the galaxy that world is in, and the universe that the galaxy is in.
You're entitled to your beliefs.
Your belief does not mean you have the right to take away the rights of others.
If you believe gays being married is a sin, then fine, that's your right. Do you believe sins should be enforced under threat of violence via law, and everyone should be jailed for all sins?
The bible is old and outdated, many common things are "not allowed" if you take everything it says literally.