Others said, "You are too young, many of you have never experienced it and are immature." I'm drunk, too, as if I don't know anything stupid. How should I reply?

In fact, the more you refute what others say, the more others will think you are naive, so I think the best way to respond is not to refute, just know who you are in your heart. There is no need to explain to others, and others will not listen, because they are not you, and they will only look at you from their own perspective and their own life experiences. No matter how much you say, it seems to them to be just sophistry. But if you just want to respond to each other, maybe you can say this:

I'm young and I haven't experienced many things, but that doesn't mean I don't know anything. Whether a person is mature or not depends on how many things he has experienced. Some people have experienced a lot and suffered a lot, but they still don't know how to learn.