1- What universities do you recommend for master of computer networks in Poland ?
None. Courses in English in Poland are very poor quality, and a diploma from any of them is not worth much, if anything, on the job market, in Poland or elsewhere.
Is "University of Information Technology and Management in Rzeszow" an accredited university ?
It's not a real university, and is not allowed to call itself a university in the Polish language. It takes advantage of a loophole in the law to market itself as a university to gullible, naive and clueless foreign students. A degree from this school is worth less than used toilet paper.
Is it possible to work and study in Poland in field of computer networks ?
If you need to earn money to finance your studies and stay, then Poland is not the country for you. It is practically impossible for foreign students to find work in Poland unless they speak the Polish language very well, and that takes several years of hard study. Make your plans on the very safe assumption that you will never be able to earn a single penny during your stay in Poland.
What cities are better to live and study in Poland ?
Unless you speak Polish very well, are able to study in Polish, and have wealthy parents who can finance 100% of your studies and stay, the forget about Poland and any other of the poorer countries of the EU with high youth unemployment: Portugal, Spain, Italy, Greece, Bulgaria, Romania, Croatia, Montenegro, Slovenia, Hungary, the Czech Republic, Slovakia, Lithuania, Latvia and Estonia.
If you can't study in a rich country, then it would be best to study in your own country.