My mom is a mental patient and her sister intentionally taken my moms' 4 acre land through gift deed

Hello, my mom is a schizophrenia patient (mental patient) since 2010 and her husband died in 2016, now she was almost bed patient and can walk only with assistance. she brought 4 acre in 2004 and 1 acre in 2007. In 2012, my mother's sister intentionally taken back all the 5 acre land through gift deed and registered by paying taxes to the government, this incident I came to know in 2019 January when I take a look in encumbrance certificate taken from meeseva. Though my mom is the owner of the land since purchase of the land, it was taken care of my moms' sister due to my dad's bad habit's(drinking). Now the issue is when I asked mh mom about gifting this land she said she had not gifted any land to her sister, which means my mom doesn't know that they had stolen the land. Also I'm an adopted son to my parents when I was less than year old. Except in ration cards, aadhar cards and birth and degree certificates, I don't have the proofs as adopted son. Now can I fight along with my mom to get our land back as it was done intentionally without knowing to my mom. If there is a provision getting it back please mention it to me.