There are tons of recipes in English for Polish cheesecake (sernik) on the internet. Search with Google.
The difference between American cheesecake and Polish cheesecake is that the former uses cream cheese, whereas the Polish version uses twarˇg, a fined grained product similar to what is called farmer's cheese in the States. You can make a suitable substitute for twarˇg by whirling farmer's cheese in the food processor until it is homogeneous. Or you can take REAL DAIRY cottage cheese, let it drain overnight in a cheesecloth lined colander until the whey comes out, and food process that.
Polish cheesecake is a lot drier and far less sweet than American cheesecake. Using the method above and the recipes on the net, you will get a decent Polish cheesecake. It might not be exactly the same as your grandmother's, though. To recreate her recipe will require experimentation and abundant experience with baking sweets to the point that you understand the theory behind each ingredient and how altering it affects the final taste and texture.