Farm land illegal occupancy by third with unregistered fraud document

I have purchased one acre of my relative land registered to me two months before.As it was lockdown for two months unable to visit the land.Recently two days back I visited the land and I was shocked that third party was seeding the land and I stopped and that got into coontraverse and I complained to local police station.The opponent came with a lawyer saying it's our land and we purchased on 1980 since then we are enjoying our ownership.(unregistered document) Actually the land has complete register History from 1950 to till date.My relative purchased and registered on 20/10/1983 .Thereafter he changed the patta to his name and never visited the land but was paying Cess fee on land regularly. I have all the records favouring for my purchase in proper and perfect manner.But the opponent doesnot have a legal documents and claims we are in possession and we have a unregistered document executed on 1980.From thereafter there is no other evidence. I have visited the land once a week atle