Sure, I can help you improve your writing. Here is a possible rewrite of your text:
Old Dick
Biggest birthday party
Tom pointed to the card that Julie had bought for Old Dick’s grandmother. “What does it say?” he asked.
Julie had just managed to buy a present and a card for the old lady, who was celebrating her 120th birthday. The next day, she went to see Old Dick, who was her friend and neighbour.
“How can she be your grandmother? You’re too old to have a grandmother,” Julie said, puzzled.
Old Dick smiled. “She’s known me ever since I was 30. I don’t remember anyone else,” he said. He looked at the card and read it aloud. “Happy birthday to the most amazing woman in the world. You are an inspiration to us all. We love you very much. From Julie and Tom.”