Actually, JWs have taught for many decades that Adam's sins could not be forgiven (nor could Eve's) since they sinned while they were in a perfect state. Furthermore, JWs believe that Jesus blood allows for forgiveness of sins. The friend that told the poster otherwise was incorrect.
However, JWs also teach that the wages of sin are death, and that the "slate " of sins is cleaned when one dies.
They also teach that the animal sacrifices offered did not actually exonerate anyone of sins - they merely foreshadowed the coming sacrifice of Jesus blood. They explain this during their annual observance of the Lord's Evening Meal (the Memorial). Some speakers have bungled it but the ones who follopw the outline seem to speak in unison.
Nevertheless, they still find ways to over-complicate each of these teachings, even when scripture seems to support their teaching. It is little wonder that many Rank & File JWs don't know what they believe.