4300 is NET
4300 net is a different story, especially as you don't have to pay much for travel and visa. As long as you stay away from the unholy trinity of alcohol, tobacco and girls, you will even have a little left over for a rainy day fund. No major savings, but at least enough to pay your way back to Italy if things don;t work out.
For people from outside of the EU, the cost of travel, visa and residency permit is quite substantial.
For orientations sake:
Studio apartment, all inclusive, rent fees and utilities: 1500 PLN.
One bedroom ditto, 1900 PLN.
Food and household expenses, about 1000 PLN. Less if you cook all meals from scratch at home, more if you eat or snack away from home a lot.
Public transit, about 100 PLN.
I won't give a figure for internet/TV/telephone because people's expectations and requirements vary widely.
Budget about 300-600 PLN for basic clothing and occasional living expenses.
So that's a minimum of about 3000 PLN right there, before entertainment and travel, and health care.
So yes, you could do it, if you are modest and careful. As for Berlin, it would be quite difficult to live the same lifestyle on 1350 Euro,