What Am I Riddles

Question: I take what you receive and surrender it all by waving my flag.What am I?

Question: I'm round at the ends and high in the middle.What am I?

Question: Give me food, and I will live. Give me water, and I will die. What am I?

Question: What's made of wood but can't be sawed?

Question: I build bridges of silver and crowns of gold.Who am I?