Need help in resolving property dispute

Religion Hinduism My father recently sold our 30 bigha land for1 crore and 20 lacs out of which 10 bigha was in my uncle's son name. My father bought this agricultural land for opening a school but the seller at first Only given him 20 bighas. He said I will not give the rest 10 bighas to my father So unfortunately we had to buy in my uncle's son name. His father has given us 5 lacs for opening the school. And 2 lacs for transferring the property in his name. I had transferred him 11 lacs to my uncle And 5 lacs to my uncle's son online Now he is saying I want more money In total 40 lacs other wise I will go to court. So pls suggest me what should I do Bcoz he has betryaed our trust.