Not getting the Flat even after complete payment.

I purchased a property in Guwahati, Assam. The property was mortgaged with the state cooperative Bank. A broker came to me and told me that the flat is for sale. I saw the property and came to an agreement with the Flat Owner and the bank. They said the Flat will be mine once the payment is made. I made the payment by cheque to the cooperative bank and not to the Flat owner. There was a tenant in the Flat and the owner said he will vacate it as soon the payment is made. I trusted him and did the agreement. The Flat is now registered in my name. It has been a year now but the tenant is not leaving the Flat as he had a three year agreement from the previous Owner and the they did not inform us about it. I only came to know about it when I complained to the police about the tenant not leaving and he brought a Stay Order from the court. I contacted the bank and found that the Manager was suspended for fraudulent activities. Initially the tenant was giving me half the rent. After the police complaint, he is not even giving the rent he used to pay before. The Flat owner asked me to give him back the Flat to which I agreed and he said he will pay me back by January 2017. But he did not pay. I told him I will do an agreement only after full payment. When I went to the police he said to the OC that he will pay in 6 months. But I know he won't. He has lied to me about everything from the beginning. Please advice me about the steps that I should take.