Help me and my gf to overcome from her family.

Hi, I am a 19 years old Trans man and I am in love with a 19 years old girl for past 4years. Her family is against us because of her cousin sister. Her cousin sister is a Nurse she didn't even know anything about Transgendered persons. She is lying and telling something about transgender people that they'll die in 5years after their surgery and hormonal imbalances. I thought that my gf's family is not okay with my gender and religion but that's not a problem. My gf's cousin sister confused my gf's family and she tried to convince my family too but my family knew everything about me and my gender dysphoria so my family didn't listen to that. Yesterday they called me and my aunt's to talk. My gf's father is quit listening to me but that sister didn't allow my mouth to open If I opened I will solve and clear all those things to him that's why she is doing like this. Her only motive is to separate me and my gf. She's already in problem with her personal life that's why she's not allowing us to live happy. And she spoke many harmful words and her words affected me mentally that's why I got hyper and shouted. My gf supported me so she went out. She told her husband that I beaten her. After sometime her husband came too fast and beaten me. They affected me domestically. Then my gf's dad apologized to me, aunt's and my gf and after seconds I am okay with that And I too asked sorry for my anger but that sister was not ready to accept it. After some conversations Atlast my gf's dad told me first you need to complete your studies then after 2years I will marry my daughter to you. Till the end of your studies I won't lookup for alliance. Whole family is against us because of my gf's happiness only her dad is going good with me. Just her dad promised to me and my aunt's in words. My gf's dad said There's one condition that you shouldn't talk to her or see. Because of this condition I am not okay with his words. So I am little scared about it. My gf is very strong and stubborn but after I left her, her mom and her cousin sister family they tortured her and she cried a lot. Again I went up and I spoke with my gf and her dad. But his promises are in words so I couldn't believe him. I thought of getting some bonding certificate. Surely, I need a bonding letter. If my gf's dad is not okay with the bonding letter can I file a complaint against him or not. Kindly help me please!