Builder payment issue

Hi I had paid 20% ( 11.5 lac+ ST) amount for 1BHK apartment in Oyster Living SRA project (www.oysterliving.com) in 2015. As per builder terms and conditions, oyster living project was suppose to start before 2017. In case any delay in the project later 2017 then they were liable to refund our paid amount with 15% simple rate of interest. Until 2017 when we did not see any single progress in the project then we cancelled our booking and asked them to refund the money but they said they cant refund our money before 9 months and also they will not pay any interest for this period. During the cancellation the booking, they asked us to return the allotment letter and gave us PDC of total amount on 29th March, 2019 as well as payment schedule. After 9 months of cancellation of my booking again, we approached them, but they refused to pay and asking to wait more until their project start. After lot of site visits and arguments, they transferred total 2 lacs ( 1 lac two times) in this month instead of 8 lac which is not as per payment schedule. After receiving this amount, we tried to contact them for remaining amount. But, asking to wait rather than commitment. We dont know that how long they will take to refund our hard earn money. Therefore, we want to know your expert opinion and choices to get this money back safely and how long it may take. Kindly suggest best choice and reasonable solution as a expert. Looking forward your reply. Mangesh L Jha +[deleted]