were growing faster than almost any other eu country
You are mostly growing because of the increasing trade volume with other EU members. Leave the union and we'll see what happens. How about losing roughly 70% of your duty free exports to the common market for a start? How about all these corporations moving out of Poland because you've lost easy access to the EU? The Brits are already rethinking their vote for BREXIT. Guess why.
worldstopexports.com/polands-top-import-partners