Friend is blackmailing with a stampaper

My name is sooraj 36years old. on 2015 one of my friend afsal gave 5.59lakhs as a deposit tomy saving bank account for commodity market (sharemarketing). Unfortunately the first month itself sales was flop and the whole amount lost. I am not a trader. but as a friend he deposited. later i gave 2lakhs to him in various instalment..after 1 year he started blaming me and threatening me that he will make trouble at my home..then i wrote in a 100rs stamppaper that i will give the 6lakhs rs back with in 6month. and given to him. but i could arrange the amount and he was not ready to adjust the loss. the oraly we made a compromise that he want 60% of the amount and rest he wavedoff. i paid the said amount by feb 2017. but now after 5 years he again filed a case in local police station and asking for the remaining 40 % ..the stamppaper is with him. that is not noterized. is there any way to get ridoff from this blackmail?i dont have any money to give to him...i didnt borrow from him..