How long has Dan learnt English?

Seven months later, Dan kept a lecture "Reading-Concentration-Success" in Bournemouth, Dorset, England. His listeners, about 50 young people, were not only from England, but also from the entire world. They didn’t know Dan’s mother tongue. However, it didn’t mind-Dan spoke English. And what’s more, he managed it by heart, without looking into a written text of his speech. The lecture lasted almost one hour and brought about a considerable success.
    Dan’s lecture took place on the King’s School of English a week after his arrival to one-month English course. At the beginning of the course there was a common placement test. Its result was surprisingly good for Dan. He gained more points than his schoolmates having been learning English for five, six, eight or even more years. Dan has had only 4 months of studying English behind him in his home country, without a teacher and performing his normal job during studying. Well, Dan’s method of studying English appeared as very proper and very quick simultaneously. What concretely brought Dan to his outstanding results?