You have received some incredibly brilliant answers, many from extremely qualified and well placed individuals too, so let me give you a foreigner's practical perspective, if I may.I was born in Italy, didn't speak a word of English when I first came to London thirty years ago, there were no 'online resources' then, and I remember going to the movies bringing a pocket dictionary with me. The problem was though, I did not know the spelling of most words I heard on screen, so I always felt like attempting synchronized swimming in a force 10 gale at sea.One day, a very old guy who was sitting next to me at the cinema, noticing how furiously and frustratingly I was flicking my well worn out dictionary, asked me how well I wanted to speak. "Like I native" I answered. He laughed and said that that was not possible, but he could teach me so people would be impressed by my English nevertheless. We met regularly and talked about all sorts of things, it turned up he was a retired professor of modern languages at Cambridge University, fluent in Italian too.He told me that the only way to become almost perfect at speaking a language, not just English, was to allow others to correct you, even constantly, as you speak. He said that that would irritate most people immensely, but surely it was the best and fastest way. So he did, and I remember these surreal and surely irritatingly stuttered conversations, that eventually became more balanced, as he interrupted me less and less.One evening we were together at a dinner party and a lady sitting next to us complimented me on my English, saying it was perfect, asking where I came from. Before I could answer he said to her, visibly irritated, that if my English was truly perfect she wouldn't have noticed.As we were walking home I asked him how I could improve further, especially my diction, so to become perfect. He smiled, hugged me and said "Franz, what makes you special and 'exotic' is exactly that, your accent and your little imperfections and odd grammar, never lose it completely, it would be a huge mistake."I was very fond of him, he taught me not just English, but a most valuable lesson too: make the most of what you have received in life at birth, it is what makes you special.I felt confident enough eventually to write several books, and I even won a Creative Review Award for my writing. Nowadays I give lectures to all sorts of audiences, and whenever someone compliments on my "perfect" English I smile and answer "hopefully it isn't, so you'll remember me better".My English is far from perfect, but it has an unique style (or so I hope) and my accent is so undefined that people cannot really figure out where I come from, and that is enough.So find someone you can talk to regularly who is happy to correct you every time you make a mistake, but at the same time don't lose what makes you special, exotic.