firm: it didn't sound right to me.
visited: the [ed} ending is stressed too hard, and the last vowel sounded like [ei] as in take.
Australian: look up online disctionary on how lian would be pronounced.
abroad: you might look up the online pronounciation dictionary for the second syllable.
if you go for General American Accent, you might check how you pronounce [t], Darwin, town.
It is very hard to give sugestions to advanced speakers, since we ourselves are also working on our own pronounciation problem.
Keep it going.