Not going over Poland, as they may have special laws, but in general in the EU, it is ok if you are a EU citizen and open a company in another country within EU. If outside the EU many (each?) countries have a 'list' of some countries they consider 'low tax' and you are forced to be taxed at home (basically, they tax you like you are a local company and have to supply all paperwork to your country of residence).

The problem is when you want to pay yourself from that company, where in general, you have to register with the tax offices in both countries (company country and your residence country and then you may be able to pay more taxes on your home country depending on many things).

Not a tax attorney or the likes, but my cousin is and deals with a lot of this as she works with some small seed funds and helps them incorporate in other countries.