Is it really true that after death people go to heaven or hell?

This is a good subject! It has been spoken and written of God that time and space, the fourth and fifth dimensions, cannot contain The Holy Trinity. It is written: "absent from the body, present with the lord", but it has also been written that we will "sleep for a time", therefore, both are true. A preacher on the radio described it as falling asleep in a way that when you wake up, it will feel as though you never slept. Maybe we will sleep in the place that God has prepared for us in Heaven, so then both would be true. That same radio preacher I spoke of earlier also calculated the size of "The New Jerusalem" that comes down from Heaven to Earth in the last part of the Book of Revelation to be large enough to house every person who has ever lived and who is yet to be born, based of course on the presumption that we are living in "The Last Days". The main point is to turn to Him who saves and repent of your sins before it is too late because some will go to eternal suffering, away from the face and blessings of God.