Roughly 'blee-una va oor'.
Sláinte = cheers (Irish); Slàinte (Scottish).
slawn-jih vah in Scots Gaelic (Good health!)
Òg-Mhadainn/h-òg-mhaidne ('new morning')
"matin vah" It means "Good morning" in Scottish Gaelic.
oidhche
Happy New Year is Bliadhna Mhath Ùr (pron. Blee-an-uh Va Oor) in Scots Gaelic. There doesn't seem to be a set expression for wishing someone a happy Hogmanay, which is New Year's Eve. Hogmanay itself is Oidhche Challainn.
It would be Slàinte mhath! in Scottish Gaelic.
meadhon-oidhche
Irish is oíche Scottish is oidhche
Scottish: Oidhche Shamhna shona dhut. Irish: Oíche Shamhna shona dhuit.
It's Gaelic. And it is spelled Dia dhuit in Irish Gaelic. It's Scotts Gaelic it's Madinn mhath, or hallo. Keep in mind that they do not pronounce their letters the same way we do in English.