Property in Potkamin, Ukraine taken by government in WW2. Can I get back.?

Here are the details, it is my grandfathers land and it used to be Poland. Then it was taken by the germans, then taken over by different countries I do not know which. Anyways, now it is Potkamin, Ukraine. My grandparents visited it in the 80's and the big house it was, is now a medical building. My grandfather got the papers still and it written in ukrainian. Who can I contact to get this back, if it is possible to do so. I have tried to find a lawyer but had no luck. Any useful information, please post.