Property Litigation - Kindly please advice how to proceed

1)As per Muslim tradition after Nikah husband(Eg. Mr. A) has to give Mehr (Gift) to the wife. 2)Mr. A has given the land to this first wife(E.g Mrs A) as part of Mehr(Gift). 3) In 1986 Mr. A has signed in the agreement that he is gifting the land in the name of first wife(E.g Mrs.A). 4)Mr.A - First wife family details i) 5 Daughters ii) 1 Son 5) Mr. A died in the year 2015 6)First wife(Mrs. A) has gifted the complete land(Gift Deed) to one of her unmarried daughter(E.g Unmarried Daughter) in 2010. 7)Unmarried Daughter sold the complete land(Sale Deed) to his brother(E.g AFirstWifeSon) in 2014. 8)ASon has sold the land to my mother(E.g Ms. X) in 2018 ============================================================================ Mr A Second Wife family members details 1) Mr A second wife name (E.g Mrs BSecondWife) 2) Mr A second wife family members details i) 1 daughter ii) 1 Son(E.g Mr ASecondWifeSon) 3)Mr A has sold 40% land(Sale Deed) to his Second wife Son Mr.ASecondWifeSon in 2011 4)Mr A has sold 60% land(Sale Deed) to his Second wife Mrs BSecondWife in 2012 NOTE: 1) During the selling time Mr.A is suffering from Paralysis and was in Second wife(Mrs. BSecondWife) home during that time(Selling land to his second wife and Son). 2) We were not aware Mr.A is having second wife. 3) we have purchased land from Mr (First Wife Son (AFirstWifeSon)) as he was paying property tax and water tax and current bill for the shed in that land. 4) Mr A is a retired central government employee. 5) ASecondWifeSon has sent notice to my mom(E.g Mrs X) claiming he is the actual owner of the land. 6)Mr A. Passed away in year 2015. Please please please help me sir all our savings are gone and also into lot of debts. Please give me advice to take any action on Mr AFirstWifeSon who sold to us and also how we can save the land from second wife son(Mr.BSecondWifeSon). NOTE: 1) I have transferred 85% money through online. 2) In Second wife/Son registered document Khaja put thumb impression as he was having paralysis. 3) Second wife/ Son hasn't taken any signatures of First wife family members while registration. Please give me advice to know the actual title owner of the land can be know 1) Filing RTI 2) Title Search Report Please give me advice can i complain against register office(For doing multiple registrations) and municipal office(As it has collected taxes for 8 years) and also what action i can take against Mr AFirstWifeSon as i have paid amount fully for the land. Please advice me sir. I will be lifelong thankful and please sir tell me how can i save my land legally and what steps i need to follow to come out of this situation.