Hinduism not only believes in existence of heaven but fairly explains the correct definition of heaven termed swarga in Hinduism. A to Z of heaven (swarga) is detailed in various Upanishads (independent spiritual treatises).
As per Upanishads heaven existed in core of sun where temperatures exceed millions of degrees centigrade. It is in such high temperatures a soul atman feels comfortable. As per Bhagavad Gita and Upanishads we are not the manifest physical being but much beyond. We are primarily a spirit, consciousness that manifest human form to remove dross impurities within.
After death of present body we as a soul atman got released. This released soul atman manifests a new body based on residual balance of karma at the time of death. If matching parents do not exist or become available on mother earth, the soul atman in the meanwhile hibernates in heaven or hell… in heaven if the residual balance of karma is positive and hell if negative.
Both heaven and hell existed in sun. Hell existed in the periphery of sun where temperatures were considerably less. Based on residual balance of karma if a soul atman is granted a seat in hell, it suffers all the time. Something designed for temperatures exceeding millions of degrees centigrade, how it could survive in hell where temperatures ranged around 10,000~12,000°C.
This confirms the saying that everything suffered in hell.
As per Upanishads sooner matching parents become available on mother earth, the hibernating soul atman immediately manifests a new body on mother earth to start a new journey of life.
The to and fro journey in the life of a soul atman from Earth to sun directly depends upon availability of matching parents on mother earth.
Contrary to what is said above, Hindu pundits and Christian clergy always promised the gullible mankind a choicest seat in heaven if they were prepared to shed reasonable amount of money in donation to the temples or church. Not knowing anything about heaven (swarga), these so-called religious practitioners made good of the blind belief of commoners, masses.
Whatever the claim of pundits or clergy, all were ignorant in matters relating to heaven. The reality of heaven can be realized only by treading path of spirituality as detailed in Bhagavad Gita.