Succession

My great grandfather and grandfather had purchased a 3 floor property and a seperate house by contributing half amount each , my great grandfather died intestate (without any wil) and my grandfather in his wil divided seperate house to his eldest son and each floor(of 2nd house) to his three sons now one of elder uncle sold his floor to a dealer and thus two floor of my father and younger uncle was unsold later on my father constructed a new house and we including my grandfather and younger uncle moved to that house Now my younger uncle 30 day prior to the death of my grandfather managed to change his wil (by taking his thumb impression) and took all the property (all 3 floors). After that he told my father that we need to sell the property as it was disputed because of the one floor purchased by a dealer so he he needs my father's signature on some paper, my father agreed and signed without studying as he has trust on him, he sold the property in 2018 and now denying to give my father his share that we never had any share in this property, after that we get to know that he had filled a case against my father in session court before selling the property and hired a lawyer from his side also where on behalf of my father that lawyer admitted the existance of that wil and then withdrew that case himself in lokadalat , before withdrawing the case court has passed the judgement of restricting my father to sell the above mentioned property untill the case is solved. before selling it he also had a deal with the dealer who purchased a floor. Now after when we got certified copies of the whole case it is evident that he took all the sumons that court issued my father as my father and mother goes for job in day time and signed on his behalf and also while filling the petition he gave address of the old property while he is residing with us from 7 years.+ in the last will of my grandfather there were two witnesses one my grandmother (she also died) another one is our neighbour whom he also lied before taking signature he told her that it is partition papers of our house so she didn't study the paper and signed it as witness( although my grandfather was not able to talk at that time) and now after this incident she is ready to accept that in court by giving statements and affidavit whichever is required.Now my questions are 1.how can I move to the court and challenge that will 2. If the second wil existed then half portion that was purchased by my great grand father how can my grandfather write a wil for that it was not his self acquired property rather it was passed to him and by my understanding I am also the one of successor of the property.( Although second will is fake).3My uncle is constructing a new house for himself from that money can I claim stay on the construction as he never had any employment or business history.4I had got a notarized copy of a contract of the deal in which amount and transactions are mentioned but sale deed amount is half.