Maybe it would help if we think of this in the way that God has revealed it.
From the beginning God reveals Himself as one.
He reveals His power and his majesty to His chosen people, making sure that they recognised that above all He is one.
This lesson has become a bedrock of the faith for the chosen people before God sends Immanuel.
Jesus, grows in wisdom and grace before God and Man, and His mother stores all the wonderous happenings that surrounded His birth. He starts His ministry with a miracle, and both His words and actions prepare his followers for his astonding claim that He is God’s Son. His followers already know that God is one, and Jesus affirms that He and God the Father are one.
Jesus is very clear that he comes to fulfil the law, and not to change it. He says that whoever sees Him sees the Father.
Jesus prays to the Father - the disciples hear the Father’s voice when Jesus is baptised. The Father and the Son are distinct, but are one God.
This is easier for them to accept than for us, for they are with Jesus on a daily basis, and can see and hear Him pray to the Father. They have their faith which tells them that God is one, and they experience the reality of two of the persons of the Blessed Trinity.
Finally, when Jesus knows that they are as ready as they are going to be, He teachs them about the Holy Spirit, as He promises to send the Holy Spirit to them.
The reality of the Trinity was taught to man through concrete experience. Even before they met Jesus, the disciples knew God the Father, who created all things. They learned to know Jesus, god’s son, by living with Him and talking with Him. They experienced that Holy Spirit when He decended on the in power on Pentacost.
What Jesus taught them in words they also experienced.
Read the openning chapters of the Gospel of John. Hear you learn that Jesus was the Word that God spoke in the beginning, through which all things were made. John clearly says “the Word was God”
God knows that without the absolute conviction that there is only one God, we would get it wrong.
It is also clear that God, Father, Son and Holy Spirit, can interact. God the Father sends His Son to save us. Jesus sends the Holy Spirit to be with his followers until the end. The Father says “This is my Son, with whom I am well pleased.”
Faced with such a reality Christians have written uncountable numbers of words! Sometimes they help us, sometimes they hurt our heads, and sometimes they just plain mess up.
I hope that it helps to go back to the actual experiences that have revealed God as having three persons while remaining one.
Trudy