There was no death in God’s original plan. Death only became part of human life as a result of the sin committed by the first human beings. By committing this original sin they rejected God. Yet God still wants us to live forever. But living forever on this earth, with all its misery and suffering, would not be wonderful at all! Jesus came to earth, died on the cross, and was brought to life again by God to undo the consequence of that first sin.
Thanks to Jesus we can live forever in heaven after our death. We can get to heaven by following Jesus, and by living in a loving relationship with God and our fellow human beings.