Acquisition of Second Language

I am half-Taiwanese, half-Japanese. My mother is from Taiwan. And when I was 2 years old, when mom had my sister in her womb, to decrease her burden, I went to grandparent's house in Taiwan for more than half a year alone. Of course I don't remember that well, but mom told me about that a minute ago.
During I was there, my cousins living in America were there too, and I was in the environment where Chinese & Taiwanese & English were dominant language, not Japanese. I got confused. And anytime my cousin tried to take my stuff, I strongly refused saying "ダーメ" meaning "You can't".
And this is the most interesting that when I returned home, and went to kindergarten, any my teacher said she didn't understand what I said. And this is how children growing with more than one language. In certain period, they stay abroad and return. I think if I stayed much longer, I might have had Japanese & Chinese. Well that could be.
I see a lot of returnees these days, especially chances increased after I entered university. And I was really jealous about that. Achieving same academic entrance, they can speak English!!
And that became much stronger last year because I took the English class where only 2 people are not returnee. At the same time, I got implication that we have something that returnees don't have while reading one article. And I felt so much better. But now, the advantage of being able to speak English fluently is so huge, that I again felt strange. But this time, with a much more optimistic way. I could be good English speaker and also good English Writer. And that me is different and could be better than returnee have. Well, just practice practice practice.
Push myself, go beyond them