It would have been nice to see the word rămas before asking us for its definition.
the response said a spune ramas bun e greu (not la revedere) what does that mean??
ramas bun means farewell
If you break the sentence into smaller pieces it comes down to 'a spune' is to say, 'ramas bun' is good bye and 'e greu' means 'is hard'. In this case they used 'e' but it could be also 'este' if I understood correct.
La revedere = goodbye
Rămas bun = so long