The trinity is a human ( man made) doctrine, an attempt to understand that nature of God and the nature if the realtionship between God, Jesus and the Holy spirit, nothing more and nothing less.
One can accept it or not, it ( the doctrine) is NOT biblical but then again, the vast majority of all man-made doctrines are NOT, they are interpreations of parts/themes of the bible.
Jesus was the ONLY begotton Son of God and NO begotten does NOT equal or mean created, Jesus is Unique above all creation because Jesus was NOT created but begotten and since he was Begotten of God, Jesus's very nature is God, it can be nothing else.
Just as we beget a child and that child is US ( Human) and we create something ( like a piece of art) and iti s just THAT ( something created) and NOT US.
God, Our Father is God, for God can be nothing else.
The Holy Spirit is the spirit of God and as such is God, for it can be nothing else.
The Son of God is the only begotten of God and as such, is God ( like a human is human) and can be nothing else.
For a brief time Jesus was fully man and still retains that in his current form also, fully man ( all that man is) and fully God ( all that God is).