Some lessons he learned [in my words]:
1] People who died and experienced their soul and came back stopped caring about material things. Amazing. A person goes to a world that is completely spiritual and thus realizes that all the gashmiyus of this world is הבל הבלים.
2] People felt that we are all connected and could no longer harm others because they felt that to harm others is to harm yourself.
3] People felt that the next world was much more real than this world. This world is עלמא דשיקרא.
4] They say that there was no time there. Even though there was a sequence of events they felt that there was no time and couldn't explain it.