Denying for Ameneties

I, recently bought a flat in Nallasopara and i have few queries against it which i want to know about how should i proceed against the builder.. Problem 1: I registered a 1BHK flat in Nallasopara on September 2018, i cleared my payments by December 2018 but the possesion was given to me on February first week.. however the builder has charged me maintenance charges from may 2018, when i had given the booking amount but due to incomplete papers provided to my loan agency by the builder my loan wasn't sanctioned by the bank and it got delayed.. When i talked to the builder about it, i was answered that due to my late payment the maintenance has been charged from the booking date. However the registered agreement clearly says that the maintenance charges will be from the date of possession but builder is just denying to pay back.. Problem 2: The builder has not given the receipt for my cash payments and has denied to even acknowledge it in written.. he also did not provide me with the details of my expenses against which i have made payments and denied to provide with that details as well.. he has also denied to give any possession notice in any form or acknowledge my request to sign the possesion notice.. Problem 3: After taking possession of the flat, i did not recieve all the amenities and structure promised to me before buying the flats as per their property brochures.. modular kitchen with trolleys, toilet in flush isn't installed even till today neither Intercomm facilities are given .. Problem 4: The infrastructure of the flat is not of the quality, the railings on the balcony is rusted and can fall at any time.. there is water seepage from my ceiling which is causing damage to my property.. one of the false ceiling in hall already fell over me due to the seepage from terrace as the building is incomplete.. Querry: Even after continuous approach and requests, builder is just denying to provide any compensation or complete the project or give any details. So i want to know about how should i proceed to file a case against builder, if i can..if yes, then and on what basis i can file a case against builder.. if so, den whom should I contact and what would be the expense for the whole case till the court gives the plea.. Thank you..