Date and amount changed on signed empty promissory note

My father had taken a debt of 1,20,000 cash from my uncle and signed on two empty promissory notes in 2016 and he paid a interest to him to 28,800 in 2018 as one year interest at 2rs/month but this transaction doesn't have any proof except he made someone in my family write in one notebook . Later he was suffered with lung cancer in 2018 and died in 2020 December . My uncle has notified about this debt in 2019 only when my father alive and asked me to pay it since i was facing financial issues i told i will pay it later on and i have prolonged it till 2021 Oct since i was literally facing financial burdens . In oct 2021 , i went to his home along with my cousin and paid him 2,50,000 rupees and he took that and said still i need to pay 1,30,000 and for that i need to sign on one more promissory note . I denied it and said my having financial burdens and can't pay anything more and won't sign on anything . There some discussion happened between both of us and we left home without taking the proof that we paid him 2,50,000 and also my father signed promissory notes. Now, he filed a case in court and court has attached my house since its on my father name . He had written date 6 months before my father died and added a sum of 3,50,000 debt in the promissory note and added two people as witness in that . How do i prove this is not valid since debt taken in 2016 and already paid by me . I don't have any proofs except transferring 1,50,000 to his son bank account and my cousin who came with me and saw i paid 1,00,000 cash to him . any advice in this case . As per court , i have to 4,87,000 to my uncle