“What was God doing before He created the universe?”……Our finite minds find it hard to comprehend that before the universe was created, God existed alone. We know fromJohn that Jesus also existed:

John 1:1

"In the beginning the Word already existed.The Word was with God, and the Word was God."

The preincarnate Christ was intimately united with the Father, so as to partake of His glory and to be appropriately called God. He has Himself explained it in John 17:5

Now, Father, bring me into the glory we shared before the world began.

We also know that the Holy Spirit was present before we were created.The Spirit "hovering over the face" of the dark and formless earth.

Genesis 1:1-2

In the beginning God created the heavens and the earth.[a]2 The earth was formless and empty, and darkness covered the deep waters. And the Spirit of God was hovering over the surface of the waters.

So, before time even existed, God existed in three Persons: Father, Son and Holy Spirit. The Trinity existed in perfect harmony and flawlessness, having all they needed in one another.

David said:

Psalms 16:11

You will show me the way of life, granting me the joy of your presence and the pleasures of living with you forever.( Greek version reads You have shown me the way of life, / and you will fill me with the joy of your presence. Compare Acts 2:28)

Before creation, God felt complete joy and fulfillment as He perfectly beheld and communed with Himself. God has and always will experience complete joy because He has complete and perfect knowledge of Himself.……So before He created the universe, God experienced absolute satisfaction in Himself. God dwelt joyfully alone in eternity as the Trinity. These three were together in fellowship with one another from all eternity. They loved each other.

Ephesians 1:4-5

Even before he made the world, God loved us and chose us in Christ to be holy and without fault in his eyes.5 God decided in advance to adopt us into his own family by bringing us to himself through Jesus Christ. This is what he wanted to do, and it gave him great pleasure.

2 Timothy 1:9

For God saved us and called us to live a holy life. He did this, not because we deserved it, but because that was his plan from before the beginning of time-to show us his grace through Christ Jesus.

John 17:24

Father, I want these whom you have given me to be with me where I am. Then they can see all the glory you gave me because you loved me even before the world began!

We know at some point they discussed the redemption of mankindbut everything else lies in mystery.