We have to use our heads and our ability to reason.

First, once we are convinced by reason and evidence that God exists, we have to determine how he/she makes him/herself known to us:
- What are reliable ways to gain information about this God?
- What are reliable written sources of information about this God?
- And how can I know?
Second, at least one way to gain information about this God is through creation—the world we see around us. Since he/she made it, it should have characteristics and clues to what this God is like. That's where a normal search for information would/should begin.

Third, the holy books certainly contradict each other in their conflicting claims about God, so I have to examine them for correspondence to reality to assess (A) if any of them are true, or (B) which one of them is true. There are many factors involved in determining correspondence to reality. I, obviously, have concluded that Christianity is true and that the Bible has correspondence to truth. On that basis I have accepted the Bible as the accurate revelation of the One true God, and YHWH as that true God.

> If belief in a God is only based on faith, then should that be enough? I don't think so.

I agree. Faith, according to the Bible, is the assumption of truth based on enough evidence to make it reasonable to make that assumption. It is not a leap in the dark or a belief in things for which there is no evidence.

Why should I believe anyone knows anything about God or even if God exists?

I don't think anyone does. There are holy books that are supposedly inspired by a God, but they have very conflicting claims about God.

If belief in a God is only based on faith, then should that be enough? I don't think so.