why did your god leave them out from understanding him?
That is a good question but I doubt you will like the answer. The ontological question is always with us because the ontology says that you can't grasp the notion of God without being God.
That we need to ask your question is the only reflection of being both a physical being and a spiritual one. If we are both physical and spiritual them the spiritual part will exist for ever. Then death is only a transition. If there is no God, as you assert, then we just stop at death but our being will experience life forever. Then death is experienced by others. For us all experience stops.