Can God only be one aspect of the Father, the Son or the Holy Spirit at a time?
When Jesus was here on earth who did he pray to?
When the voice from Heaven spoke saying this is my Son in whom I am well pleased who was speaking?
I'm confused, sorry.
No. As Christians we must believe that Jesus Christ is "of one Being with the Father" whence proceeds the Holy Spirit.
When Jesus was here on earth who did he pray to?
The Father, with Whom He is eternally One.
When the voice from Heaven spoke saying this is my Son in whom I am well pleased who was speaking?
The Father, of Whom He is eternally begotten.
I'm confused, sorry.
Don't apologize; we're all confused about the Trinity. As God, the Trinity is beyond the capacity of human reason to understand; The Catechism of the Catholic Church puts it this way:
"The Trinity is a mystery of faith in the strict sense, one of the 'mysteries that are hidden in God, which can never be known unless they are revealed by God'... To be sure, God has left traces of his Trinitarian being in his work of creation and in his Revelation throughout the Old Testament. But his inmost Being as Holy Trinity is a mystery that is inaccessible to reason alone or even to Israel's faith before the Incarnation of God's Son and the sending of the Holy Spirit." [CCC, 237]As Christians, we are not called to understand the Holy Trinity; we are called to accept It by Faith. Please pray for the strengthening of my faith, as I will pray for you.