You should try to make friends that can only speak English, or another language that you don't know and English. That way in order to communicate you HAVE to speak in English. This was the most important part when I learned any language. Also it helps to go to an English University where you'll be forced to really understand everything in the langauge, from grammar to speaking, to different types of English (business, technical, etc). There's a range of schools you can go to, I go to WSB-NLU in Poland. There's the possibility to learn English and the tuition is really cheap, plus they give an american bachelors upon graduating.
It's a business school in the south of Poland (2hrs south of Krakow). I found it online and upon visiting I immediately applied. I'll be graduating this year, so I'm living proof that it's a good school.
Do you have any Polish highlander in your family? You wrote Nowy Sącz and I immediately thought Zakopane... so many highlanders from Zakopane went to US :D
I wish you GOOD LUCK with your exams!
Oh I see you're from Poland.. the full name is: Wyzsza Skola Biznesu - National-Louis University. It's in Nowy Sacz.