In Ulster, I think people would say "go ndéanaidh a mhaith duit" /go N'eni: (ə) waixˈ ditˈ/ and the other expressions you said. In standard Irish you'd write "go ndéana" but I think it's a Connachtism, because in Ulster you pronounce this -a like -aidh before subjects that aren't personal pronouns (and -aidh is the historical ending, -a is a simplification of it).

There's a nice one you've not mentioned : ná l(e)ig ar d'aná(i)l é (don't leave it on your breath).

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Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

Not so much a simplification, I think, as a contamination into the absolute ending -aid from the conjunct form -a.

(The old conjunct form goes back to the old secondary ending -et, while the absolute form has the old primary ending -eti)

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Not a native speaker.

Always wait for at least three people to agree on a translation, especially if it’s for something permanent.

My translations are usually GU (Ulster Irish), unless CO (Standard Orthography) is requested.

Tá tú ag m'fhoghlaim! Tá'n ceart agad, is é an -(a)idh an deireadh is úire agus is cosúil go dtáinig sé faoi anáil an aimsir fháistineach nó rud ineacht mar sin, mar go rabh -a i Sean-Ghaeilg agus i nGaeilg Chlasaiceach. Chonaic mé -aidh mar dheireadh i dtéacsannaí a scríobhfaí sa 19ú haois nó mar sin agus chreid mé gur rud ársa a bhí ann, ach charbh eadh.
Go rabh maith agad

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Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

Go ndhéanaigh (níl ndéana) mhaith duit!

Go ndéanaidh a mhaith duit

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Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

I thought - "go ndéana" was used for prayers and blessings ?? Módh fóthuiteach something??

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It is recommended that you always wait for three to agree on a translation.
I speak Connemara Irish, and my input will often reflect that.
I will do an mp3 file on request for short translations.
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It is, yes—it’s the subjunctive mood (an modh foshuiteach, which is just a calque on the Latin: sub- = fo- + -ject(um) ‘thrown/placed’ = -suite), which means ‘may XYZ happen’.

In Old Irish, all verbs had both absolute and conjunct endings, which where used in different contexts, and the endings were a bit different (the conjunct ones being shorter and more compressed). The subjunctive in the third singular (i.e., ‘may (s)he/it do XYZ’) had the absolute ending -aid(h); but the conjunct ending -a.

When Irish eventually lost this silly distinction between absolute and conjunct forms, they were rather randomly distributed: sometimes, the absolute form became the more common one; other times, the conjunct form became the more common. And in some cases, like the subjunctive here, some dialects generalised the absolute form (Ulster), while other dialects generalised the conjunct (everywhere else, basically).

With this particular verb (déan, which has always been hopelessly irregular and bothersome), the Ulster form is a more recent innovation: Old Irish never had a subjunctive ending in -aidh in this verb. The absolute form was do·gné (which has been lost), and the conjunct form was -déna (= déana).

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Not a native speaker.

Always wait for at least three people to agree on a translation, especially if it’s for something permanent.

My translations are usually GU (Ulster Irish), unless CO (Standard Orthography) is requested.

Lughaidh, seo dhuit kokoshneta. Kokoshneta, seo dhuit Lughaidh.

Go maire sibh a chéile. Sílim go mbeidh muid uilig a' foghlaim ón mbeirt agaibh, ní amháin faoi Ghaeilge Uladh ach faoi Ghaeilge go léir.

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Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).

GRMA Koko

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It is recommended that you always wait for three to agree on a translation.
I speak Connemara Irish, and my input will often reflect that.
I will do an mp3 file on request for short translations.
___________________________________________________________

Koko > an avatar do chuid Dhennis King thú?
Is beag duine ar an idirlíon a bhfuil eolas aige ar a' tSean-Ghaeilg

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Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne