Good Riddles

Question: I break down buildings I crumble mountains You can't see me What am I?

Question: What goes up and down but never moves?

Question: What goes around comes around?

Question: I am important at the most dangerous times. I can not be seen, heard, or smelled. If you use me too much you would fatally die. What am I?

Question: "Good morning!" - I appear again! Time for breakfast - I`m long as F*** Its dinner time - I`m crouching down Supper time approaches - I`m on my tippy toes "Good night!" - ...gone again... What am I?