I'm sure other members will have good ideas about which changes to make, and may disagree with some of mine, but here is my input.
1. "The man told him that someone had to sign the papers anyway, so my father had no choice but to sign for it."
This sentence wasn't clear. Did the father have to sign the papers themselves, or was he just signing something for the postman to acknowledge their receipt. The context here will change how the sentence should be written.
2. "You are a grownup man."
This isn't a phrase I'd use in BrE. You have a variety of choices: "You are a grown man [now].", "You are an adult [now].", or just simply "You are a man [now]. I'm sure people will think of others they might use instead.
3. "..on the street and calling me...": I have changed on to in, because that is how I would say it in my regional variation of English (BrE). I'm not sure if on would work in AmE, and so our AmE speaking members can comment about whether that works for them.
4. "...but I hated its representatives.": This didn't work for me, because to me a representative conjures up the image of a company "rep" going round selling things. I struggled to find the wright words and finally chose "main heroes", simply because I couldn't just use heroes, as I know in Communism a worker can be a hero as well as a leader and so that word on its own wouldn't work in that context. I couldn't use leader without having to change the sentence that follows this one, and leader works perfectly there.
Student or Learner