Agricultural land dispute

Am umarani,from madurai tamilnadu. my grandfather property(agriculture land) of 7 acres[ 80lakhs worth] in madurai belongs to 6 persons( my father (84yr old) and 5 daughters and am the second daughter). 15yrs ago , my father alone made a selling agreement with a person (rajasekar)[we 5 daughters didnt sign in that agreement],after that agreement was made rajasekar occupied our land and was not ready to give the amount specified in that agreement, since he behaved like this , my father said he wont sell the land , so rajasekar filed a case on my father in the court . To solve this matter, my father went to his sister's son(sridar) for help , sridar said to my father to sell the land to him , so that he on his own will solve this land dispute,so my father made my 3 sisters alone( last 3 sisters ) to sell the land and they even signed the documents in the register office and gave to sridar [ without getting any money from sridar ] [ note: me,my 1st sister and my father didnt sign in that document ]. But sridar was a fraud , he did not give the money for the land which we sold him and didnt even ask rajasekar to leave the land , but rajasekar is occupied our land for 15 years without giving us any money[one year before we won the case(which was filed by rajasekar)] , and now sridar is saying our full land belongs to him ,[even though only 3 of my sisters alone signed and gave the documents (me,my elder sister,my father didnt sign)] ,sridar is neither ( ready to get the 10 lakhs from us and to move out of the land) nor ( give us the full money for the land which we sold him). since sridar is behaving like this and to prevent him from occupying our land,my father didnt ask rajasekar to move out of the land, so that sridar cant occupy our land when rajasekar is there. My father has borrowed money from so many people , so he is in urgent need of money to settle all the debts , for that he should sell this land only , so for that kindly tell us , how should we file the case in the court to get our land back ???