Property Written in My fathers name

Hi , This is regarding a property we hold in kerala . My Gradfather was having a hosue and 50 cent of land in kerala . His wife passed away 4 years ago and since then he is staying alone there . He is having One son ( My Father) and two daughters all of them are well settled . Unfortunately My father passed away this feb due to illness and thereafter my grandfather passed away by end of last month . Immediatley after my grandfathers death both sisters are claiming that one was promised 25 cent and other 10 cents but none of them any document . But My moms has the copy of property in which it is clearly mentioned that in 2008 it self my grandfather has written the whole 50 cent and house to my dad . We came to know about it recently since we didnt show much interest . Now the original papers are missing . Now the questions are 1. How can we retrieve the original papers? 2. How can we transfer the property to my moms name as my dad is no more ? 3. Since both sisters of my father are claiming .Is it necessary to give some share to them legally ? 4. If at all they go for a case demanding share can we still have the possession of the property even thought the case is on . 5. Can we file an injection