The three monotheistic religions

The three monotheistic religions-- Judaism, Christianity, and Islam-- all purport to share one fundamental concept: belief in God as the Supreme Being, the Creator and Sustainer  of the Universe. this concept of the Oneness of God was stressed by Moses in a Biblical passage known as the "Shema", or the Jewish creed of faith: "Hear, O Israel: The Lord our God is one Lord." (Deuteronomy 6:4)
It was repeated word-for-word approximately 1500 years later by Jesus when he said "...The first of all the commandments is, Hear, O Israel; the Lord our God is one Lord." (Mark 12:29)
Muhammad came along approximately 600 years later, bringing the same message again: "And your God is One God: there is no God but He, ..." (The Qur'an 2:163).
 Christianity has digressed from the concept of the Oneness of God, however, into a vague and mysterious doctrine that was formulated during the fourth century. This doctrine, which continues to be a source of controversy both within and without the Christian religion, is known as the Doctrine of the Trinity. Simply put, the Christian doctrine of the Trinity states that God is the union of three divine persons-- the Father, the Son and the Holy Spirit-- in one divine being.
 "...we worship one God in Trinity, and Trinity in Unity...for there is one Person of the Father, another of the Son, another of the Holy Ghost is all one...they are not three gods, but one God...the whole three persons are co-eternal and co-equal...he therefore that will be saved must thus think of the Trinity..." (Athanasian Creed)is a Christian statement of belief focused on Trinitarian doctrine and Christology.
Let's put this together in a different form: one person, God the Father + one person, God the Son, + one person, God the Holy Ghost = one person, God the What? Is this English or is this gibberish?