If you were addressing an individual, you could say: 'Slán agus go n-éirí an t-ádh leat'. If addressing more than one person, change 'leat' to 'libh'.
In Irish Gaelic Slán (pronounced "slawn") would be goodbye.
Slán Alena
In Irish:Slán [slawn]
Beannacht leat, a Dhaid.
The Irish for hello is "dhia guit" Phonetically pronounce gia gwuit
Slán go fóill a thaisce
"Hello" in English: "Hello". In Welsh: "Was Hael". In Italian: "Salve". Can't help you with Irish (Gaelic) I'm afraid.
In Irish it's "slán le saol beo"
You need to specify Irish Gaelic or Scottish Gaelic: they are two separate languages.
Irish (Gaelic): Dia dhuit (Hello) and Bain sult as. (Enjoy) for one person. Dia dhaoibh and Bainigí sult as. (for more than one) Scottish Gaelic: ???
Irish Gaelic has seanchara (old friend): the closest Scottish Gaelic found is seann-eòlach (old acquaintance)
It's Gaelic -- probably what was meant was "Mar sin leibh an-drasta" which means "Goodbye, for now". "Mar sin leibh" = "Goodbye" + "an-drasta" = "for now". This is in Scottish Gaelic (Gàidhlig), not Irish Gaelic (Gaeilge)