HOW CAN WE UNDERSTAND GOD/THE "OTHER" OR KNOW IF HE/IT "IS"?
Simple, he knew you'd ask that question so he answered it if YOU care to look.
Do you think a creator an infinite, omniscient, omnipresent, holy, just and loving creator would create mankind in his image and not reveal to mankind after humanity's fall from God, who he is and everything mankind needs to know about creation, why he was created, why things are not as he created them, God and God's plan for mankind?
If he didn't he wouldn't be who he says he is in His Word, the Bible, a creator of infinite wisdom and intelligence whose ways are not man's ways, a creator who exists outside and inside this universe, with no beginning and no end.
God is incomprehensible to the human mind yet he has gone to great lengths to reveal what we can understand about him and his plan for His creation, sending Prophets, His Word, His Son, raising up a church of believers to spread his word in the face of an evil foe, Satan who has perverted scripture from the beginning and raised up "religions" to deceive and lead mankind down the path to destruction.
It is no secret God has reached down to man but man has rejected His plan and followed after false Gods, false teachings, false saviors and submitted mankind to the god of this world, Satan.
These are not my opinions but what God has told us himself through His Word, the Bible, according to His ways not man's.
Disagree all you want, he has put the truth right in front of your face and unless you read it, study it, heed it and listen to the voice of God and not the voice of the world you will be destined to be lost for eternity, without the presence of The One who created you, the great I AM.