How to recover money when have all the proofs of transactions

My father loaned Rs2 lakhs to her colleague on an interest of 2.5%. This was recorded on a stamp paper of Rs50 which was brought and drafted by the witness in his handwriting, who also acted as the mediator in the deal.My father's colleague also deposited her post office passbook as a security which was taken back after sometime citing various reasons. Just after paying interest for a month the mediator cum witness came forward with an idea to sell his land(it was bought next day by him after the loan) to my father instead of returning money. For this he further took 1.5lakhs. He wrote down this transaction on a piece of white paper of which I have photocopy. On this paper he forged signature of my father. Later on he started demanding more money for registering it. Recently we got to know he has sold that land to someone else. Now he doesn't talk to my father regarding it. Whole incident is less than 3 years old. Please suggest legal course of action both criminal and civil?