Sales deed

Hello sir/mam i will try to write my question as short as possible we are 3 members in the family my elder brother and i and mom my mom has been visiting a so-called Muslim baba since 2012 Recently we came to know that mom has sold the farm and another land to that baba and it took place in September 2012 itself. the property is a heritage. its been gifted by my paternal grandfather to my mom. now when we confronted mom about it she says he told mom that he will build madarsa there so gift it to us but this baba tricked my mom and registered as purchased instead of charity donate when my mom came to know about this mom asked him to return the land and farm then he threaten mom that he will murder me and my elder brother after that moment my mom just went silent. And also in documents, he wrote just 1 lakh to land and 5 lakh to but the market value of the land and farm goes beyond 50 lakh but the weird part is not even this 6 lakh was given to mom (because the been brainwashed that its a donation to build madarsa). This deal was kept hidden from both of us (me and my brother) a local lawyer has told us to go for cancellation deed. as they didn't had children permission while this event took place. first mom should have ask us. but she is 65+ easy to fool. and that baba is there to loot such people. my brother i not sure what is the right and time-saving steps to take.