How to get our remaining property from the same Survey No. after selling a part of it to the builder

Hi, my father and his brother inherited a property from my grandfather and according to the partition deed both get 26.5guntas each out of 52.5guntas plus Kharab of 1.5 Guntas. Meanwhile my uncle (father’s brother has got 27.5 Guntas entered in the RTC by bribing the revenue officials) . In 2016 my father & his brother sold their shares to a single builder, wherein my father sold just 25guntas out of 26.5guntas of his share and his brother sold all the 27.5 guntas . During the negotiations the builder had executed an MOU (not registered)to my dad tat 1.5 Guntas of his share will be left on one side with access to construct a Temple, which we very badly construct. But we failed to mention this 1.5guntas in sale deed schedule. Now tat it’s been 3years the builder says my father has no share left and we can’t construct any Temple in tat property, in fact he also have demolished a small size temple which my grandfathers had constructed. Now what should we do to get that 1.5guntas from the builder for constructing temple ???