凄い /su goi/ (and 素晴らしい /su ba ra shii/ both) can be used meaning 'awesome, magnificent, amazing etc'. Pronounced su like in suit, go like in ego, and i like in ray.
"Arigatou" is pronounced ah-ree-gah-toh. The handy thing about Japanese is that it's pronounced just the way it looks! (A 'u' after an 'o' just means a slightly longer 'o' sound.) Or you can say...