Property Dispute- Cancellation of Gift Deed without Court Fees

I need you advice in the below matter if you can advice me it is highly appreciated Subject : Property Dispute I need adivice from an expert. My Grandfather is having 3 child. My father being the eldest, one sister and one younger son (my uncle). Unfortunately my Grandfather passed away on Dec-2019 ,he is suffering from paralysis since April-May 2019 and was not well since then. My Grandfather staying with us since last 24 years untill August-2018 then he moved in my father's sister house (my grandfather feels at that time that he will get better facilities in my father's sister house). Now the WILL which was done in April-2019 is in favor of my father's sister and we got a notice from court in 2021, and we challenged the Case is currently ongoing issues will be framed in the next hearing it is in the Karkardoma Court (we have our Lawyer for this case). When my Grandfather got admitted in hospital in April-May-2019 my father's sister did'nt told us about where our grandfather is admitted. We have to reached out to Police and they found the hospital where he admitted. It tooks weeks to find him. So we are thinking this has been done in some pressure. Here 75% of the belongings of my grandfather now belongs to my father's sister and my father along with his brother's family challenged the Will. Also to the above my Grandfather was admitted in the hospital for months and he did a Gift Deed for one of the biggest Property in favour of my Father's Sister (to note he was discharged from hospital and taken for the gift deed and after 2 days of this deed again admited to hospital) so have these proofs. Now my Father's Sister sold that biggest Property to someone and they were chasing my Father and Uncle for NOC but we didnt signed any NOC , so they just sold that property in Oct 2022. My quesitons is below, 1. Can we challenge this Sale Deed ? 2. If we can challenge the Gift Deed then the Court will be huge(~15 Lk) considering it was a big Property in Delhi, so is there any way we can have some remidiation to this as we cannot pay this much as court fees, But would like to have Justice ? This case needs to filed in Karkardoma Court. Please suggest me if anyone can help.