I didn't revise the events or length of your story at all, but it's totally grammatically correct now.
The story takes place in the barricaded city of Weimar, Germany. There’s a zombie out-break and Vivi, our main character, is in the hospital. This takes place in the summer, because things like “it is so hot today” and “I can’t remember the last time we had a summer like this,” are said in the book. Mrs. Warner has taken Vivi to her therapy room to talk to her and give her her pills. She pulls out strawberries.
“I thought no one grew them anymore.” Vivi says, surprised. It’s hard to grow things here nowadays. Mrs. Warner pulls out some hair dye. “It was hard to find,” she says, “but I managed to get it. I want you to color your hair.” Vivi disagrees, yet she dyes it pink.
At night she hears a strange moaning noise. She falls out of her bed and sees a confused old man, asking to turn the music box up. Mrs. Warner sends him back with locks. Vivi, feeling creeped out by the light, goes inside and looks for him. The “music box” the old man spoke about ended being a brick. When she hands it back to him, he throws the brick and tells her to run.
Vivi goes to the train station- she wasn’t allowed to be there, so she was hiding. She sees Mrs. Warner and a girl named Eva.
“Train ticket, please.” Vivi stutters, confusedly.
Eva says, “You aren't very bright, are you?” She looks out the window. “I could say there are unicorns running out there, and you’d believe me.”
They both board the train. When they get to a random stop, Eva says she will run away without her, but when she does, she gets attacked and calls for help. When the zombies come, Vivi grabs a medicine bag and opens it. Eva ends up saving her
The next morning, Vivi shows her the camera she fixed. Eva is mad that Vivi went through her stuff, but they keep walking on their journey and talking about what happened before the zombie outbreak. They sit on a roof and look out at the sunset to see giraffes walking.
“They must have escaped from the zoo in Erfu,” Eva exclaims. “I can’t believe they’re alive two years later!”
They find a castle-like house nearby, explore the strange-looking inside, and eat the fresh veggies they find. When exploring they could tell that the people who lived there had not been gone long; they left nothing useful. There were chairs and long sleeve shirts tied together. They heard knocking.
“There could be zombies in there,” Eva said.
Vivi watched Eva start to hit the door. Vivi runs to see what’s going on, but when she hears yelling she gets scared and ducks to the ground. Eva leaves to go outside by the bridge for a breath of fresh air. Vivi runs over to meet her.
“What’s your problem??” Vivi exclaims, and pushes her in the water.
But there were zombies in there, and they were pulling Eva down. Vivi picks up a rock and throws it, even though she was scared to. Eva survives, but she’s so angry that they split up.
Later, Vivi walks into a garden and sits in there, looking around and playing with a ladybug. She finds some cake and eats it, but she’s sad to find out it’s a man’s cake with weed in it. He saves her and gives her a little home. She works for him until one day she finds something: it was Eva, buried in the ground. Vivi digs her up and they run off. Halfway there, they find zombies. “Run and jump over the gate,” Eva says.
Vivi runs and finds a dog. The dog follows her everywhere. When getting to the place, she stops and says, “They will not like you here, Eva.” She was dirty and affected.