Property Belongs To Government

Hi, Our Father has bought a Land (27X45) in 2008, from the respective Site Owner(the whole Land is Divided for 8 Persons[27X45], we bought elder son portion ), it has been Registered to our Father in Municipal , khata also has been made, and my father is paying every Year Government Fee also. In March 2014, we sold the land to other person and made a registration to them, their all of a sudden after 20 days, They started saying that the municipality is not making any khata to our name and we are not getting Licence from same. so we decided to give back there money and we made registration cancel and re registered to our father name. Same type we asked with the Real owner , but he said all are correct and i am unable to pay your Money Back!! The Issue is Only with our whole portion and a half portion of other party, Now the Municipality Saying that in 1962 the marked portion belongs to Government , Produce the Documents such as Government Yearly Fee receipt if it is owned by you!! they given Some old Xeroxed documents, Ufff i am unable to read or understand those Documents. My Question are, 1. Why Municipal Made a land registration and Khata to Real Owner and as well as to my father name also 2. Why Land survey officer approved the Land Sketch 3. up to till date why Municipality has not put a board there such as Marked Portion Belongs to Government, Something is phishing here, we are unable to understand Now, What are the minimal options we can go with current Situation, as none of our family doesn't knows Rules and regulations of LAW, Government ACT[we consult the Lawyer's also, their also we are getting Dual Opinions/answers] As a second step i am asking Initial help from This forum, 1. What are all the valid/genuine documents do i required to Fight in Court Thanks, Anil