Im a 18yo asking advice about family environment

Hello i am a (M) 18 years old, I have a sister who is 17, and a 28 years old brother from my fathers previous marriage. Every relationship in the family is tense at the moment because of my brothers academic situation, basicly my big brother 10 years ago made a big success in the exam in our country that you take to attend university bu being among the %0.4 something like that and started studying computer engineering at one of the top universities in the country, he struggled without us being there in the city with him and even though he is brilliant like he is a really smart person he struggled because he did not willingy go there he just went there because it was an upcoming engineering branch st that time and it was basicly the best thing he could have studied with that exam result. Long story short he couldn’t graduate and went through a lot of stress had to go to therapies, phycatrists; had to take antidepressants other hard drugs etc. He was really hurt and he came back facing a lot of pressure and when he was gone my parents often went hard on us. (me and my sister) My father is a drinker, he would never hurt us physically but mentally I think he scarred my sister. I was always pretty good at school and i attended the same exam my brother did and got a decent score, enough to go to a paid university’s electric engineering faculty. You could say that the only sibling that doesnt do well in school is my sister. I often think the reason for that is the fact that in elementary school my father yelled to her a LOT because she couldn’t do basic math, I love my father but i hate the way she treated my sister and my brother over pure academic stuff. Anyways back on my brothers story he came back, took the exam again. Didnt do that well this time and started to study “english teaching” at a local university. But he was much better, less stress, less pressure, being close to the family and stuff. 2 years later government takes a decision and decides students who have left or gave up on their past college can re-attend it no questions asked. This sparked joy in the family and everyone started asking my brother if he is going back to engineering. He only has 5 lessons he needed to pass and with this pressure coming again he said he would do it, The university im attending is also really close to where he is going to go back to so my father started to look for apartments at rent and they thought he was %100 sure about going back. Just yesterday my brother decided to talk to my mother about how he wants to stay and he feels stressed about it all. Everything just turns backwards like life is over and we are going to lose everything we have, my mother starts shouting to my brother and when i go to confront her about her behaviour and ask why she is acting like this she says something like “go to hell all of you i dont care” shouting, leaving the house. Now today no one is leaving their room and in breakfast my mother decided to argue with my brother over this university stuff and tells him to just go away to our aunts house near the university while there is still a month or two till they open. They shout again, argue and go back to their rooms. I hate the situation at home right now and I dont know how to talk to my mother, father or anyone. That is why I am typing this out the anonymous people on internet to see what they think and what should I do. I am worried about my sister who is going to take the university exam alone in the house because her brothers are not going to be home and I cant even imagine the stress she will go through. I am tired of this pressure to accomplish in school all while my parents are filling my ears about not being like my siblings whom I love with all of my heart. I want to try everything i can to fix this problem and let there be peaceful environment where everyone can be happy, any advice would help me a lot, thank you.