General Information:
EU-Community: https://www.daad.de/de/laenderinformationen/
EURES-Portal: https://eures.ec.europa.eu/index_de
Visa:
Visa types and requirements: https://www.msz.gov.pl/en/travel_to_poland/visa/visa
Entry and residence requirements:
Ministry of Foreign Affairs: https://www.gov.pl/web/dyplomacja
Social insurance provisions:
ZUS - Social Insurance Institution: https://lang.zus.pl/en/
Ministry of Labour and Social Policy: https://www.gov.pl/web/rodzina
Accommodation:
Just landed - Housing & Rentals: https://www.expat.com/en/housing/europe/poland/
Bed & Breakfast: https://www.bedandbreakfast.eu/en/c/798544/poland
Country information:
Wikipedia: https://en.wikipedia.org/wiki/Poland
Doing Business in Poland: https://www.biznes.gov.pl/en/firma/doing-business-in-poland
Culture Crossing: http://guide.culturecrossing.net/basics_business_student.php?id=165
Further information:
Poland Travel: https://www.poland.travel/en