What to do when someone fraudulently execute a registered sale deed

Somebody has executed a registered sale deed on 2000 in my agricultural land. The land was purchased by my late mother in 1980 and mutated on 1985 and till 2017 tax paid. Upon verification of sale deed of the party we found : 1. Seller name is mentioned as my mother name 2. We have 1 acre land but sale deed executed on 1.2 acre land 3. Seller thumb impressions are not numbered in sale deed 4. On original copy it is written exclusive possession whereas in certified copy written peaceful possession. 5.Seller signature on top of every page in original copy whereas as in certified copy it is bottom of every page. 6.That time taisildar signed as wittness on sale deed. 7.Our sale deed numbers and how my mother has got ownership not mentioned in the sale deed of 2002. 8.My mother has not signed any document ever and she was uneducated Please suggest