He asks: “What did humans eat during this early period of the Garden of Eden?” What can Creator tell us?

The human diets of the first human cohort were not so different from today. There was a quite similar array of plant and animal life on the Earth in that earlier era, and people lived close to the land for most of the time. Today, only at the very end of human civilization have you become a technological race and living in very large numbers. In the first go-round, humanity was not so rapidly evolving because life was challenging, and later on humanity was heavily subjugated and kept in check by being a slave race quite early along. That was done openly and with a heavy hand. That as well limited growth of the population. In general, the diet was more natural and healthier in the absence of agricultural technology, factory farming, worldwide commerce for foodstuffs necessitating widespread use of preservatives and other adulterants in food. But, as with today's world, even though there was starvation at times in that first go-round, the problems ultimately were being subjugated by extraterrestrial beings who were psychopaths, and saw humans as having no value, and they were ultimately discarded through extermination.