* As an adjective meaning "good" or "healthy": gut
* As an adverb meaning "well" or "good": gut
* As an exclamation meaning "well!": na ja! (more informal) or nun! (more formal)
* As a noun meaning "well" (as in a source of water): Brunnen
So, the German spelling of "well" can be gut, na ja, nun, or Brunnen, depending on the meaning.