God(Yahweh) done answered your doubts in His Son 500 years before the Quran corrupted it!
The Deity(Jesus Christ) is Elohim(God) the same as the Spirit of Elohim(Yahweh) is Elohim(God) or that the Word(John 1:1) is the same as Elohim(God).
The Deity(Jesus Christ) existed before the foundation of the world!
John 1:1.
The Word(John 17) is in the Father and the Father is in Jesus.
So since Jesus is the Word(John 1:1) then Jesus is also in the Father.
Jesus Christ who is sitting at the Right hand of the Father has been given all authority, judgment(John 6:27), and etc.
Everything has been placed under His feet in Heaven and on Earth
(1 Corinthians 15:27).
And in the end when all things shall be subdued unto Him(Jesus),
then shall the Son also himself be subject unto Him(Yahweh)
that put all things under him(Jesus),
that God(Yahweh) may be all in all(One),
with no arguments that He(Yahweh) is one
from those who are lost and don't want to receive the truth.
1 Corinthians 15:16-28, Deuteronomy 6:4-5.
Jesus shall humble himself again in Heaven and prove that he is the Son of God to the terror of every Muslim when they are thrown into the Lake of Fire buring forever because of their unbelief!