English is my native language. There is no reason for that. One doesn't choose one's mother, or one's mother tongue, but it was a fortunate choice in many ways. You can travel over the world, or do business almost anywhere in English. However, I think it is also a choice that made me lazy about language learning. Most people in the world have much more incentive to learn a second language.
I learned smatterings of a few languages: Spanish, German, Russian, but I think I can only claim to speak Chinese, and even that is a limited kind of speaking. I can converse, but I don't understand every word I hear, and I often express myself awkwardly.
I started studying Chinese, because I had many Chinese co-workers, and I just wanted to say a few words to be polite. Later, I got interested in learning Chinese for its own sake. I still strive to improve, but I started late and I don't live in a Chinese environment. So, I will probably never achieve a native speaker's full capability.