Did you think the Christians could help you here? Jesus never specifically said it was possible to get to Heaven after one lifetime, by any means. The Christian doctrine is from Paul, not the Lord Himself. The Christians can only relate to you what Paul has claimed.
Jesus talked about Heaven 19 times.Luke 6:23Rejoice in that day and leap for joy! For indeed your reward is great in heaven.We can get everything we need to know from Jesus in the Gospels and not just Paul.