Builder's untimely death related dispute

Hello, I am seeking guidance here related to a case which is being fought in the civil courts of Nainital against a builder property dispute.The history of the case is that my parents who belong to Nainital were seeking an under construction property which was being constructed by a local builder in the premises of the Nainital town. It was a 2BHK ground floor flat.The total cost of the floor was agreed upon on Rs 40,00,000 out of which an amount of Rs 22,50,000 was paid by my parents to the concerned builder in three instalments through cheques of Rs50,000, Rs 2,00,000 & Rs 20,00,000 respectively. The builder had taken the authority of the land from a 2nd party who is also a local resident of the town and had given the power of attorney to the builder. The agreement between them was such that because of being occupied in different businesses the overall responsibility of the land was given to the builder by the second party for any kind of maintenance, construction ,local authorities matter etc through the said power of attorney. The builder however could not pay to that party at the same time, hence the registry for that land was never done on the builders behalf by the second party. The construction kept on getting delayed and in the meanwhile the builder got sick & unfortunately died. The wife & the relatives of the deceased builder initially said that they will return the money in instalments from their end but even after almost one & a half year not a single amount was released from their end. Eventually they started saying that they had no clue about the money and are in no position to return the concerned amount. Meanwhile the second party from whom the builder had taken the land sold the property to a third party as no stay order was issued on the property by the court at that time , the third party then started their own construction there in the disputed area. We were thus forced to file a case against the builder's wife & daughter as being his legal heir it is their responsibility to respect the agreement which my parents had done with the builder according to which either they should complete the pending construction of the floor and handover the property in exchange of the remaining Rs 17,50,000 or else return the money given to the builder along with the interest. This case also involves the 2nd party asking them to either complete the construction against the remaining amount or else to not sell it to anyone else because of the ongoing dispute against the property. Now the case also involves the third party to whom the land was sold by the second party for construction purpose. It has been 3 years now (including covid) & not a single argument has happened till date, only further hearing dates are given. My parents are very old & had invested all of their life savings on this.Would request some suggestions here as to how can we further take this case forward & come on a positive conclusion. Thanks