How can i change patta and fmb sketch as per sale deed documents

Hello sir, My family live in a 940 square feet home. The house was built in 1945. We bought the house in 1984. In 2003 only we get patta for the house. According to our sale deed documents, the house is 940 square feet. but Patta has only 820 sq. feet. My parents didn’t noticed while getting patta?. The FMB map(sketch) dimensions of the land is also wrong. NOW we are looking to rebuild our house. But the backhouse(rear – house owner) person making a problem that we have 1 1/2 square feet in our land. But in that place we have kitchen and the bedroom right now. Our compound walls are having 940 sq.ft exactly. Before We Bought The House (1960s-1970s) The place is 1680 square feet. The owner has sold part of the house at 940 sq ft (front) to one person and the remained to another (rear).both houses in a different street. we bought that 940 sq. Ft. house in 1984. We have been living for almost 36 years. But now only he’s (backhouse) making problem to rebuilding our house . He bought his (backhouse) house just after we bought it. In his sale deed documents mentioned 740 square feet. but as per patta he’s having 850 square feet . he got(applied and got) patta before us. The land map(sketch) was misinterpreted at that time and they left unchanged it. What can we do to change this. Our house walls(compound walls- all corners) in exactly 940 sq.feet. 1) What should be done to change the patta as per the sale deed documents? . 2) The map(fmb sketch is also wrong. How to change it? . The person from whom we bought the house still he live’s in near to our house. He’s saying this house is 940 sq.feet . The size of the house we are in is 940 square feet. So is it possible to change the fmb sketch and patta? How can I change it? help me What is the procedure to make this changes?