Briefly tell me what story Niels told in the article.

Write a story about a 14-year-old boy named Niels, who lives in the south of Sweden. He doesn't like reading and learning, and he is mischievous and likes to play tricks on small animals. One early spring, Niels' parents went to church. He played a trick on an elf at home and was turned into a little man as big as a thumb by the elf. Just then, a flock of geese flew through the air, and a male goose at home also wanted to spread his wings and fly with the geese. Niels clung to the goose's neck in order not to let the male goose fly away, but he was taken high into the air by the male goose. From then on, he rode on the back of a goose, followed the wild geese and traveled all over the country, flying from his hometown of Skone to the northernmost Lapland province, and it took him eight months to return. Riding on the back of a goose, he saw the beautiful scenery of his motherland, learned the geography and history of the motherland, listened to many stories and legends, and suffered many risks and hardships. During his roaming, he learned many advantages from his traveling companions and other animals. When he returned to his hometown, he became a tall and beautiful boy and a gentle, kind, helpful and hardworking boy.