Is it mandatory to sell the property if i have got partial amount

My father wanted to sell a property and talked to a person .he was ready to take my property for 12lacs but in the starting he gave us 8 lacs and made a notary ( not in the presence of registar) stating that 8lacs has been given &4 lac will be given at the time of registry and no time limit has been specified now after 3 years in feb he gave the left amount 3lacbut now we don't want to sell the property so they are planning to file a case against us .even we are ready to give fd rate as interest on 8lac but they are not ready to take and want property so I want to ask whether in court's judgement we have to sell property or money taken can be given back .so give me possible suggestion how to own my property. Thank you