Gf cheated on me and friends think it’s okay?

So first of all I’m 20 years old.
I have / had a giant friendgroup. We would hang out with around 8 people all the time. Than I brought my girlfriend in. We were almost 2 years together. Than out of nowhere she broke up with me. On the same day she slept at a friend house. I was thinking maybe she was only there to get me out of her mind.
But friends later told me that they are dating now.
It was unbelievable at first. They even told me that one time I was not with them they even cuddled a little bit. I don’t understand why they didn’t tell me. I feel hurt. I know these guys for over 5 years and still they don’t tell me this? Worst part is that she always begged me to not leave her or cheat on her. And now she does this? Wtf. This was my first relationship. It hurt me so bad. She broke up with me 1 month ago. I don’t have any feeling for her anymore but I hurts to think about that she replaced me with a good so called friend of mine. I’m full of anger. The worst part is now that my so called friend group is doing things without me. They ignore me. They even told me to just move on and be friends again with my ex and her new friend. Should I pretend nothing happens or what? What the hell is even wrong with them. They just say it’s not that deep and shit like that. They even tried to protect her new friend. Like it was her fault. I’m so done. It’s insane. Why me why do I have to experience only bad things in my life. It’s so fucked up I simply don’t know what to do anymore. I lost my Gf my childhood friensgroup my happiness. I try to move on. I work a lot on myself but every evening I think about this shit. It hurts so much to see that they are doing anything without me.
Does someone have any advice what to do?
How to meet new people and build new connections?
I’m an extrovert and I can’t stand the feeling of being alone.