Property possession related

Respected sir, I purchase a home in 2013 from a owner of that house and we give all of the amount of that house and also the resigtry and all legal document of that house is my name also the nagar nigam tax is also paid my self at the time of purchase that home.also i take loan from a bank for purchase that house and we regularly paid a installment of that loan monthly and we still live in a rented house.later we get the information about the owner that he was belong to a criminal he wants too more money for giving possession on that house.for that we call to cm office,also giving a two to three time application to the police station of the related area but it doesn't work.also we have giving application to i.g of police but it doesn't work.sir i am belong to middle class family now what can i do to get free from that situation as soon as possible.sir please help me i don't know what can i do also i have know idea about the laws and its regulation related to that.