Since we're writing stuff... (totally fictional so apologizing if the psychology isn't good enough or etc.) Kat

So here is a story from me. I'm gonna think about it as writing, so forgive me if I have inconsistencies.Here we go:

This story starts with my 9th grade teacher coming in. It was the first day I met him. He was kind and gentle, like he was the idol of all teachers. Guess they all loved him. You should understand that I wasn't one of the brightest students. I was a 15 year old, just trying to fit in and belong somewhere. We didn't have much money back then, and the neighborhood wasn't exacly the safest place to live but my mum tried to hold on. It would be easier for her to take care of us if we weren't "us". I was just a waste of space.But I had a little sister, two years younger than me. Because I left the school for two years, we were in the same class.
Our teacher was an old school guy, but different than others, like trying to get under out skin. Anyone has never done that before. Some would pretend to care, but in this neighborhood, no one would care. Except him. Most of us owe him our lives.
The way he looked at us, the first minute he walked in, and the last time I saw him, barging out in a hurry,anxious. It was so different, but I never felt anything those times,as I should have.
The first time we sensed he was different was the first lesson with him, but when we knew him was the gang fight. It wasn't unusual for us to see or join gang fights, but it was in the school, ended with some kid threatening to detinate a bomb. He talked to that kid, he was only 12. The kid fell for it. He saved the school, although we didn't like it at the time.
My little sister was 15 and I was 17 when a gang member barged into out house and held us at the gunpoint. He was powerful and had his back covered, but we had no one. At least we thought so. He wanted to take my sister. My mum wasn't home and I tried to protect her, I got shot. When I woke up at a hospital, he was asleep next to my bed. When I tried to get up, he woke up and explained me things I didn't wanna know. I had a surgery because the kid had shot me through my liver and they couldn't find my mum. Also not my sister. She was found at a dumpster a week later, overdosed some illegal drug, near death.Raped and thrown out like a piece of garbage. After that incident, I swore I'd do anything to protect my sister and my mum and I joined the rival gang. I left the school and got a gun. I shot those gang members and they weren't as lucky as me. The police never made an arrest on anything as always. When I was 20 I heard the talks about that gang wanting my sister and I rushed to her class. It was his class. I barged in and looked for her. She wasn't there but right after me, the principal came and told the teacher that my sister had committed suicide,probably preferring to die then to go with them. He left in a hurry, but I didn't feel anything. There was nothing left to feel.
After her death, I could never really put myself together. He helped me get up and stay alive but now, after 30 years, when I look back, I see my mistakes.It never ended,the darkness still remains. My sister never left.

I'm so sorry, please forgive me, you were the only one that cared and now, you're the only one I want to say goodbye to. You were more than a teacher, or exactly a teacher,teaching us how to handle life. But sorry, after my mum dying in the asylum, I got nothing here, my existence was wrong from the beginning, but I did my best. And this is the story of my life.