"So without outside help ,long adventures are impossible??"
Bunta, nobody can hike long distances while gathering their own food.
Early migrants or explorers of North America took pack animals so they could carry a ton of food. In some cases they may have stopped to hunt big animals like bison or elk, but that entire process would take days of hunting and drying meat. These animals would yield massive amounts of meat that their pack animals would carry for them. Hunting animals that are small enough for a quick meal or to carry in your pack for a few days is not the most time/energy efficient way.
Mountain men had cabins where they could settle and gather/hunt from. When they left their cabins to hunt, trap, or make a long journey to civilization for supplies or to sell furs they carried their gathered food with them and would not waste too much time gathering along the way.
There were people who could live in the wilderness. They were hunter/gatherers who lived that lifestyle for their whole life. These people had tribes to help them out. Were you raised as a hunter/gatherer? I'm guessing not.
There are also people mostly living off the land in Alaska, but they have homes, guns, fish nets, snowmobiles, heavy traps, ect. and they plan their harvest in the summer so it will last through winter.
Do you know how to hunt? Can you track animals and set traps? Are you an expert on the edible and medicinal properties of plants? Can you safely identify mushrooms?(an important food source) Will you be hiking in a place that actually has animals to hunt? Can you legally carry a gun and hunt while in Greece?
I think hunting and gathering while hiking is a good idea, but only as a supplement to the food you already have. While hiking it's easy to spot and gather edible plants on route to your destination. If you are hiking off trail you will inevitably see animals that you could shoot while walking towards your destination. You can fish lakes when you stop to rest in the evenings.
But you can't actually stop hiking to hunt and gather, it doesn't work for hiking.
In order for that to work you would need to stop, kill a large animal, and have a pack animal to carry the meat.
If you want to live off the land, that's very cool. But don't try it on a hiking trip. Plan a trip where you are camping in one spot for an extended period of time.