[Brodiaga]

^Is was going to ask OP the same question. I have a Russian friend who used to teach English in South America. His English is pretty much flawless (much better than mine), but he has a bit of a Russian accent and uses his Russian name. As a teacher, he was more popular than many native speakers, but he would still get questions from time to time about his heritage and nationality. He spent most of his adult life abroad, though. I don't know how a Polish guy like OP can learn English so well in Poland.