How to lodge a complain against harassement by a builder?

I am going through harassment by builder and unregistered association The Builder had sold property in 2013 to first buyer who was in peaceful possession for over 9 years. In 2022 I have purchased this property from this 1st buyer under Resell as Second Buyer. Now Builder is sending me mail and threating me to pay pending Sinking fund around 5 lakhs rupees indicating first buyer had not paid it. I have no dues from first buyer in my sale deed and I did not buy property from builder. Pls. advise 1. Can builder approach me for pending Sinking fund directly - as I did not buy property from Builder but from 1st buyer? 2. What shall I do if they raise this invoice in my name indicating due of 5 lakhs , as first buyer is not responding . I am paying monthly maintenance bill in time .Can they (Builder and Managing Committee) cut DG and Water supply at my home? Builder is one of the most corrupt builder of Bangalore.