We see this complex unity clearly in the passages from the New Testament we read together earlier. Now get this. But if that's true, then God can't be a simple God. He can't be a god who is one person. Well, if he's personal and loving, if, as the bible says, God is love, then he can't have existed as a loving personal God from eternity, because there was no-one to love.
Personality requires relationship.
He can't be both personal AND eternal if he is a completely singular being. To be Personal you have to have another Person to relate to. If God is a purely mathematical oneness, a monad, as the theologians call it, then he only becomes loving and personal after he created us. It means he needed to create us to have a relationship. If God is Allah, the god of the muslims, who is indivisibly one, then he might be all powerful, but he can't be loving, and he can't have a real personal relationship with us.