I am traveling right now, I see a lot of different and interesting stuff, I try a lot of new food, I meet wonderful people around...
And still I really feel like everything is just... I don't know, maybe empty... Meaningless...
I don't feel like growing up...
It is normal ? How can I enjoy more my trip ?
For the record I am traveling in China with three good friend, however my Chinese is below poor and talk with local most of the time is impossible...
When you're with even one friend, you have a tendency to ignore the outside world and focus on each other. The more people, the less interaction with the place you're at. Imagine the extreme example you see all the time of a dozen English friends (or Spaniards, Australians, or Israelis) on the road, loudly engaged in socializing with one another, not even interested in talking to any other travelers outside their tight group, let alone any locals. Ask one of them for a good story from their trip, and the best they'll be able to come up with is the one about Steve downing twelve shots and falling into the pool.
Go by yourself, though, and a few things happen. First, you're outside your comfort zone a bit more, with nobody to rely on, so experiences are a bit more intense. Second, even as an introvert, you eventually need some form of human contact so you go into what I call "emergency survival social mode" where you strike up conversations with people in situations where normal you would have sat silently and finished his beer.
But mostly, you're a lot more approachable when you're alone. That means that the locals will actually come up and talk to you. I once pulled my motorbike over to the side of the road in Thailand to find a convenient bush, and when I got back to the bike, a local guy pulled up to ask if anything was wrong (in Thai). A few minutes of awkward dictionary-assisted conversation later, I was following him back to his village, negotiating dirt footpaths on the bike on the way to have a lunch of dried fish and seaweed at his stilt house and meet his family.
Not a bad day, all around. And it definitely wouldn't have happened if there were six of us in a pack.
So yeah, ditch your friends for a couple weeks and go find a way to get out of your comfort zone a bit. I bet you'll come away with a ton of good stories!