Despite I heard many variations of answers which are six years or ten years or it's too complicated to learn, I believe that this question has no answer. I mean that no one can say "I know all in this subgect" there is always something new to learn. I'm a native Russian speaker, I'm an engineer and a manager, I'm also a teacher and I don't dare to say I know all in the Russian language. Because there are many areas of using language, many specific themes, many different directions of literature etc. And I'm not going to be a linguist. But what I definitely can say is that I can use Russian language. I can use it in my job and life. And the main thing if I need I can use Russian language to learn Russian language. I mean that the main purpose of learning is to use a target language. So I guess we should ask when will I be able to use Russian? I'll try to answer. I'd like to say - right away. But unfortunately it's not always possible. Probably a rare person is able but it's not about me. We always need time to get something new. I'm absolutely sure with right method you definitely become fluent in half year maybe more because everyone have to do in own pace. And it will be possible to use Russian somewhere in this time frame. But it's not years and years.