Unauthorized/ illegally / encroached Occupied My house property

I have a flat which i gave on rent to a tenant with written and signed contract with him regarding points covering damange, bill payments and 10% increment of the house rent per year. However after 1 year he refused to increase the rent begging us not to that year and we obliged but the same happened next year as well. Now as per the rental agreement we asked him to find some other place and leave our property within 1 month as we had made a deal with a client to sell it but now its been 2 months and he is yet saying that he will be needing 15 more days with utter rudeness and no promises. Even sometimes he use to threaten us that he will not be leaving our property and challenged us to do whatever we can do and that he will not leave the house till he find another place whereas in the agreement it is clearly mentioned that he has to leave the house in 1 month only. This is making it very difficult for us to fulfill the deal which will be a very big loss for us as we were to use that money to pay the loan my sons have taken on another property. Please suggest a way forward and also let us know how long will the process take and the shortest way to do so.