Rules of entry to Poland
As the beginning of the new academic year approached, you can check rules of entry to Poland at the website of the Polish Border Guard: https://strazgraniczna.pl/pl/cudzoziemcy/covid-epidemia-koronawi/8578,Outbreak-of-coronavirus-rules-of-entry-and-stay-on-the-territory-of-the-Republic.html
If you come to Germany first and then to Poland (e.g. you come to Berlin by plane and then you go to Szczecin by bus), please also check the entry rules to Germany. Here’s a website that may be helpful: https://www.auswaertiges-amt.de/en/coronavirus/2317268
