Cultivator occupied my 4 acres land

Cultivator occupied my  4 Acres Land

The history of this my case  is total 8 Acres of Agriculture land my grand father given on my mother `s name in 1980 the land is in Adilabad district Andhra Pradesh. In 1985 two persons took the 8 acres land as a cultivator ( kashtkar )  on 500 rupees per year agreement.

Then after in 1995 some of 4 Acres land government purchased from my mother  25,000 per acre immediately we received 50% amount from the government remaining 50% received in 2013 through the lawyer .

From 1995 to till date remaining of 4 acres land the Cultivator not giving any amount of their agreed yearly fixed amount of Rs. 500 and now the land is their possession, since 15 years the land not able to cultivate anything  land comes in cities population and now able to construct homes or school , college, etc. one person died into cultivator now all 4 acre land under one person`s son in law`s possession, and  the all documents available on my mother`s name …

The cultivator trying to making illegal documents on his name and not giving possession to us…

One of our lawyer also dealing this case since 1995 but he is not able to doing the case immediately final to in our favour  he his old man about 76 years … And now mother`s age also about 67 years.

Dear  honorable Lawyers & Experts Please Advice me what should I do now in this situation of case

And what will be the value amount of this 4 acre residing constructible land in the border of city adilabad district Andhra Pradesh –

Thanking You Your Reply Would be highly appreciated