Dont try to comprehend things which is beyond the capacity of your brain. Imagine a kindergarten student questioning Albert Einstein about his Theory of Relativity. The amount of knowledge the kindergarten student has, is not enough for him to understand Einstein's Theory of Relativity. His incapability to understand the said theory doesn't affect the validity or existence of the theory.
If you can imagine the gap of knowledge between the kindergarten student and Albert Einstein then how much more would be the gap between us, human beings and God.
Even the great Albert Einstein said "Science without religion is lame, religion without science is blind." If you can say that you have accomplished more than Einstein or you are more knowledgeable than him, then that's the time you can ask this question again.