Theory:

The story is about a man in Spain. He read many books of knights and noblemen. He even imagined himself in that era and tried to act like them. People thought he was a madman, but he enjoyed with children and told them stories about the knights.
 
shutterstock_781332670.svg
 
The man named Don Quixote is the main character who asked Sancho, another man from his village La Mancha, to go on an adventure with him, and that if he agreed to be his servant, Don would give him an island as a reward. Sancho agreed and went along with him. First, Don saw a windmill on a hill and thought that it was an ogre. Don attacked the ogre and hit himself. Secondly, Don saw a fleet of sheep and lambs and imagined them to be an army attacking them. He retaliated, and the sheep started running hither and thither. The shepherds hit him with stones.

Finally, he came back to his house and never ventured out on his adventures, as he came to his senses and knew that whatever happened was part of his imagination.