Okay kiddo, let me explain it to you in a simple way. Maxime, McDuff, and McDo are three different things.
Maxime is a French boy's name. It means "the greatest" or "the best". So if you know someone named Maxime, it means their parents thought they were the greatest baby in the world!
McDuff is a Scottish surname. It means "son of Duff" or "dark-haired". So if you see someone with the last name McDuff, it means their dad or grandpa was named Duff, and they probably have dark hair too.
Lastly, McDo is a shortened version of the fast-food chain McDonald's. You might have heard of it before - it's the place that sells burgers, fries, and chicken nuggets! So when someone says they are going to McDo, it means they are going to McDonald's to get some food.
So there you have it - Maxime is a name, McDuff is a last name, and McDo is a nickname for McDonald's. Did that help?