Did Jehovah create the world by Himself?

John 1:1-3, 10, NWT

In the beginning was the Word, and the Word was with God, and the Word was a god. This one was in the beginning with God. All things came into existence through him, and apart from him not even one thing came into existence…. He was in the world, and the world came into existence through him, but the world did not know him.

All things came into existence through who?
Colossians 1:15-17

He is the image of the invisible God, the firstborn of all creation; because by means of him all other things were created in the heavens and on the earth, the things visible and the things invisible, whether they are thrones or lordships or governments or authorities. All other things have been created through him and for him. Also, he is before all other things, and by means of him all other things were made to exist,

By whom were all things created in heaven and earth?
Hebrews 1:2-3 NWT

But in the last days he has spoken to us by means of a Son, whom he appointed heir of all things and through whom he made the systems of things. He is the reflection of God’s glory and the exact representation of his very being, and he sustains all things by the word of his power. And after he had made a purification for our sins, he sat down at the right hand of the Majesty on high.

Who made the systems of things?
Who sustains all things by the word of his power?
Isaiah 44:24 NWT

“This is what Jehovah says, your Repurchaser, Who formed you since you were in the womb: ‘I am Jehovah, who made everything. I stretched out the heavens by myself, And I spread out the earth. Who was with me?’

Who created the heavens and spread out the earth?
Isaiah 42:5 NWT

This is what the true God, Jehovah, says,
The Creator of the heavens and the Grand One who stretched them out,

The One who spread out the earth and its produce,
The One who gives breath to the people on it
And spirit to those who walk on it:

Who created the heavens and spread out the earth and gives breath to the people?
Nehemiah 9:6 NWT

You alone are Jehovah; you made the heavens, yes, the heaven of the heavens and all their army, the earth and all that is on it, the seas and all that is in them. And you preserve all of them alive, and the army of the heavens are bowing down to you.

Who alone made the heavens and the earth and all that is in them?
Job 9:8 NWT

He alone stretches out the heavens And treads on the waves of the sea.

Who alone stretches out the heavens?
1 Corinthians 8:6 NWT

For us there is one God, the Father, from whom all things are and for whom we exist, and one Lord, Jesus Christ, through whom all things are and through whom we exist.

What are “all things”?
So Jesus is BEFORE all things?
Through whom do we exist?
If the Bible has no contradictions and Jehovah says he created everything by himself but we're told Jesus is the one that created everything, what does this mean?