JFK is about 25 minutes to LGa without Traffic
If Traffic 40 minutes
Also you will have to Get your Bags and Clear US Customs in JFK which can Take at least 1 hour .
SO 1 hour for Bag and Customs.
40 min for Travel to LAguadia
Than 1.5 hrs to Check in yoyur bags at LGA and get to your GAte
Total time 3 hours and 30 minutes minimum
JFK Poland