Registered Lease Residence in Kolkata

Dear Sir, We have taken a residential flat of approx 600 square ft in 2003 on lease for 75 years. The landlord / muttali is not doing any maintenance for last 2 years. We are paying the monthly rental plus maintenance charges in advance also to him. There is total dis - unity amongst other tenants for reasons not known to me. This way the landlord is taking full advantage of the situation. The lift is not operational for more than a year now. The water reservoir has not been cleant for over a year also. There is no security and main gate remains un locked 24x7. The entrance is never cleaned and stray dog shit is all over. There are other several issues which are also health and life hazard. I personally have on several occasions informed the landlord but he takes no heed. I need advice on 2 things : 1) How do I get these problems fixed? 2) I would like to vacate the premises, how do I dispose this off and will I get market rate for the property as I had also paid market rate when I took the same on lease? Thank you in advance.