The question is probably as old as time itself.
When the Apostle Paul was doing missionary work in Athens, Greece he ran into that problem.
So Paul stood in the midst of the Areopagus and said, "Men of Athens, I observe that you are very religious in all respects.
23"For while I was passing through and examining the objects of your worship, I also found an altar with this inscription, 'TO AN UNKNOWN GOD.' Therefore what you worship in ignorance, this I proclaim to you.
King David seemed to be having his own problem in:
Psalms 27:7 Hear, O LORD, when I cry with my voice, And be gracious to me and answer me.
8 When You said, "Seek My face," my heart said to You, "Your face, O LORD, I shall seek."
In the beginning was the Word (Jesus), and the Word (Jesus) was with God, and the Word (Jesus) was God.
John 1:14 And the Word (Jesus) became flesh, and dwelt among us, and we saw His glory, glory as of the only begotten from the Father, full of grace and truth.
John 1:18 No one has seen God at any time; the only begotten Son who is in the bosom of the Father, He has explained Him.
So if you want to know if God is real, then you get your answer from Jesus Christ Who came to earth from God, the Father, and returned to Him.
From Pastor Walter G. Johnson of Shakopee, Minnesota