Land exchanged without proper documentation and now decreed

My grandfather purchased some property from Farmer in 1978. The khasra no. is 830 and 831 and 871 in the title. The walls were consutructed post purchase. My grand gather plated some guava tree and started watering them. Now in 1996, someone purchased the adjasant land and post 6-8 months, filed a civil suite stating my grand father threatend them that he will encroach his land and finally did that constructing the walls. when we received the summons, we came to know that in land revenue records, our area(covered with our walls 40 years ago) has area of Khasra 826 which we do not have title. we also came to know that the tile no. 871 is somewhere else. We had an commission report, of 1981, which says the walls are there, which we submitted as evidence that this is false that we threaten and constructed walls, we had walls way back in 1980 and possessed this land. but Judge did not consider this evidence and decreed contestent. We have to file an appale..... Can you please suggest, what should we make some extra prepration for turning the decree around.