Gift Deed Registered on my sister's name by my mother it can be filed

My father has purchased land on my mother name, now my father had died in 2013, my mother has given Gift Deed with registered doc. to my elder sister on 25-1-2020, but the original document is with me as my father has given that documents to me to take care but without my notice and without original document my mother has registered Gift Deed to My elder sister, so it can be challenged in court of law or not, and also the original land document is with financier from long who has given loan amount for interest that has to be paid to financier (the amount has taken to build 2nd floor), Please help me how can I suit a case in civil court.