My mother was divorcee. She got engaged in a live in relation. M11t1.

My mom was divorcee n she wanted to marry second time.after creating accounts on Bengali matrimony, divorcee matrimony she started to get proposals!! After few days she choose a guy who lives in Mumbai n was convinced to marry him.the guy promised to take d responsibilities of my mother along with my responsibility. After few days we moved in Mumbai on 13 to Oct, 2018. 8 months have passed. He is having sexual relation with my mother. But he has not done the registry. Now regularly he is torturing me and my mother physically and mentally!!, n wanting us to get back to our previous place. Which is currently not possible. We lived in kolkata. So while shifting here my mother brought all her furnitures with her. N now the guy is giving murder threat n harassing us physically and mentally. So what steps can we take against the buddy??