Title Suit of 2016

I have sold a 2 BHK flat in 2012 wherein I have stated in the Sale Agreement that the registration should be completed within 1 month. Due to paucity of funds the buyer failed to complete the same even after 4 years & instead sent me a Summons from the Civil Court accusing me of not agreeing to register the flat. The agreement was made only in the husband & wife's names whereas the draft copy of Conveyance Deed mentions the son's name also which is why I refused & requested the same be amended as per names in the sale agreement. Instead a Title Suit was filed against me by the son in 2016 after the demise of his father & is still going on till date. Simultaneously, a criminal case was also filed against me which was terminated in my favour last year since all the accusations were proven wrong. Now that both husband & wife have expired, can I terminate the sale agreement even though the son is the legal heir. I have visited the court umpteen times & have spent several thousands of rupees but don't seem to find any headway being made in the case. My lawyer does not explain things to me clearly too & keeps extracting money from me only. Kindly advise me as to what recourse can I take as this case is taking a toll on my health both mentally & physically as well. I would also like to mention that the purchaser took possession of the flat forcefully by cutting my locks & also removed my electric meter & installed a new one in his name. I have been paying all taxes for the same flat even till date. Request your legal advice immediately please. Thank you.