Christianity affirms that God is real, and the creation is real, but they are not real in the same way, or order. There are levels of reality, and the ultimate level is God. The "real world" exists not as an extension of God's essence, but as a separate, external, derivative reality. God is spiritual, infinite and eternal; the real world is physical, finite and mutable. "The world will pass away, but my Word will never pass away", Jesus said.
A man can be the father of a child -- the complete, 100% father -- but that does not imply that the child is a part of the father, or that the child will obey the father. That is the kind of created world in which we we exist.