In Welsh, you can say "Cadwch y gwaith da" to express "keep up the good work." Another common phrase is "Parhewch â'r gwaith da." Both phrases convey encouragement and appreciation for someone's efforts.
da
Prynhawn da,.often pronounced P'nawn da, is "good afternoon" in Welsh.
ffrindiau mawr
Cael amser da.
Mwynhewch eich gwyliau.
Dw i'n dda iawn!
"You are Welsh" = Rwyt ti'n Gymreig
The only person who would understand what you said would be a Welsh person, so what good would it do you to know how to say it?
Nos da, tywysoges.
"Nos da, Tad"
Ffarwél gyfaill da.
nos da a chroeso