God has no beginning
Age measures how long something has existed from its beginning. That works for people, planets, and even angels, because they are created. But Scripture presents God differently. Before there was a world to measure time in, God already was.
Moses addresses God as the one who existed before the mountains and before the earth was formed, and calls him everlasting (Psalm 90:2). So the most direct answer is that God is not extremely old in the usual sense. He is eternal. There was never a time when God did not exist.
Before the mountains were brought forth, or ever thou hadst formed the earth and the world, even from everlasting to everlasting, thou art God.
Eternal does not mean distant
It can be hard to picture someone with no starting point. We live inside days, years, birthdays, and deadlines. God sees time differently. Peter says that a thousand years and a day are not experienced by the Lord in the same way they are by us (2 Peter 3:8).
That does not mean time is unreal or that your life is too small to matter. The eternal God is also described as dwelling with those who are humble and contrite, bringing life and restoration to them (Isaiah 57:15). He is beyond time, yet he is not beyond reach.
For thus saith the high and lofty One that inhabiteth eternity, whose name is Holy; I dwell in the high and holy place, with him also that is of a contrite and humble spirit, to revive the spirit of the humble, and to revive the heart of the contrite ones.
What about Jesus?
Jesus was born as a human baby in Bethlehem, so his human life on earth has a real place in history. Yet the New Testament also teaches that the Son existed before creation. John says that the Word was present in the beginning, was with God, and was God, and that all created things came through him (John 1:1-3).
Christians understand this to mean that Jesus is fully human and fully divine. His earthly birth was not the beginning of his existence as the Son of God. Paul likewise says that all things were created through Christ and for him (Colossians 1:16).
In the beginning was the Word, and the Word was with God, and the Word was God.
Why this matters
God's eternity means he is not fragile, temporary, or caught off guard by history. He was God before your first day, and he will still be God after every empire, fear, and unanswered question has passed. Revelation describes the Lord as the one who is, who was, and who is to come (Revelation 1:8).
You do not need to solve every mystery about eternity before coming to God. Start with what Scripture makes clear: the Creator has no beginning or end, and he invites people to know him. Reading Psalm 90 slowly is a good place to keep exploring.