Suppose that a supernatural being like GOD has to exist to explain nature, what makes you think that... ?

God has revealed his nature to us and that has been recorded in scripture:

God is eternal, that is without time...which is part of the fundamental nature of God and is expressed in the concept of God's simplicity. Which you can look up if you want a fuller understanding.

The Big Bang is the creation moment, and aligns well with the biblical view of creation.

There is no nothingness, there never was a period when there was nothing. God is, that is why he is called eternal, God was, is, and will be. Our frame of reference is bound to the universe and its time, since we, along with the universe are finite and temporal.

So the question of "before God" is meaningless, because God exists in the place of nothing, thus nothing and a beginning for God is not possible. But God is the beginning of all that we know because we belong to the universe which was created by God. All the laws and properties of the universe that we know are about the universe which was created by God, God is not contained or constrained by what God has made. Since beginnings and endings along with time are fundamental parts of our universe we can not escape them, but since God is the maker and is greater than our universe, God is not bound to the same rules.

Cosmologists believe that the Universe, and with it space and time and every thing it contains, appeared and expanded into being some 13.7 billion years ago at the Big Bang, and that it has been expanding ever since. Scientists know that the Universe had a beginning and the laws that govern it will produce an end to the Universe.

Isaiah 43:10

“You are My witnesses,” declares the Lord, “And My servant whom I have chosen, So that you may know and believe Me And understand that I am He. Before Me there was no God formed, And there will be none after Me.

Isaiah 42:5

Thus says God the Lord, Who created the universe and dispersed them out, Who spread out the earth and its offspring, Who gives breath to the people on it And spirit to those who walk in it,

Isaiah 44:24

“I, the Lord, am the maker of all things, Stretching out the heavens by Myself And spreading out the earth all alone,

Isaiah 40:22

It is He who sits above the circle of the earth, And its inhabitants are like grasshoppers,

Who stretches out the heavens like a curtain

And spreads them out like a tent to dwell in.

Isaiah 45:22

“Turn to Me and be saved, all the ends of the earth; For I am God, and there is no other.

Isaiah 66:1

Thus says the Lord, “Heaven is My throne and the earth is My footstool. Where then is a house you could build for Me? And where is a place that I may rest?

Jeremiah 23:24

“Can a man hide himself in hiding places So I do not see him?” declares the Lord. “Do I not fill the heavens and the earth?” declares the Lord.

1- I was not "brought -up" as a theist, but became one later in life.

2- nature did not cause itself. Nor did it begin without a cause.

That means the cause must be transcendent of nature - aka "supernatural".

God (the Judeo-Christain understanding) does have the necessary attributes, both philosophicly and scientifically, to be that cause.

God is the best explanation for not only the existence of the natural world but also its many attributes we see and experience.

If you have a better line of reasoning I should like to hear it. My email link is open.

First, that supernatural being can be tested because He left a Word that can be checked.

Second, the finite demands an infinite.

I only want to know one thing, how much time, effort and study have you applied to this subject to arrive at your conclusions?, as they seem to be the result of a dream you may have had last night.

If God wants us to know Him, then He would have to have some means to reveal Himself. And so we have the Bible that talks about how to know Him.

It relates to what is called mind control and self-hypnotized brains.

They are told it, they accept it, they can't handle possibly being wrong.