Hi Mario
Not sure if Poland is part of the EU in flying legislation but I have a medical taken in portugal which is a European Union class 2 medical. I have a UK PPl. I
The medical states that it complies with ICAO standards.
It should be valid in all the EU countries. You should not need to transfer it. Point this out to you flight training organisation. But good luck with the Irish paperwork, best not to go there if you can avoid it. ( I worked there for 5 years so have some experience) The approach is the same in Portugal, best not to ask as it is easier for a civil servant to say no as then there can be no come back.
Good luck.