Ancestor Property Occupied by Strangers

We have ancestor property of 18 acres near Hassan in Karnataka. initially I don't know about this when I visited village after long period of time people use to say the whole 18 acres belong to my grand to grandfather.Then I visited the taluk office and told records guy to pull all the records for the particular survey number below are the data I got from him. 1.From village accountant the Index of Land form 6 which clearly shows my grand to grandfather name and total 18 acres along with this he pulled old Pahani in the Pahani its clearly mentioned its Ancestral property.I know based on Land revenue records I cant prove ownership what I did I told him to pull the EC from 1951 till 2019. 2.Now I got the EC I shows some transactions regarding sale of Land but none of the transactions says my grandfather name as seller there are different guys who sold bits and parts of the land. I am stuck here now what to do Can I file a case based on the available documents or do I need to pull any other documents. Please advice.