Do you know about Quora? It’s one of the best social networks in terms of questions and answers. Needless to say, there are numerous questions and answers about the English language. This is a particularly good example:
What can a non-native speaker do to achieve native fluency?
Time and practice.
“Native” (in the sense of language) means to grow up speaking the language in natural, native-speaking surroundings: that is, with and among others who have grown up under exactly the same language conditions. Unless that happens (or happened), a learnt fluency will always be slightly off (even by the slightest margins) when compared with the real thing.
A foreign language speaker learning English will never attain true native fluency.