Thanks to my effort I progressed quickly and when I noticed that I was starting to fall behind the group I asked the school if it was possible to change the group and despite my fears everything went very smoothly and I was able to continue my studies. I had a foreigner for a teacher so I couldn't communicate with him in Polish and at that level it was a great solution.
After 1.5 years I got a job in a foreign office. In such a short time I was able to pass the interviews and start working in an international corporation. Of course my English still needed improvement. So I continued my studies with a native speaker. After two years I can highly recommend Fluentbe to anyone who really wants to improve their English.
You can read how the lessons look like on the website and I have no objections to that, but the way they deal with the student and adapt to his needs is worthy of praise. I wish you good luck and perseverance.