How would I say "Except for English, Irish is the language I speak best."

My best guess is

Ach amháin Béarla, is í Gaeilge an teanga go labhraím is fearr

I'm fairly certain of my attempt up to "teanga" but after that, I'm just taking an educated guess.
Any corrections or suggestions?

What you need is a relative clause, a direct relative clause because teanga is its object, so: "a" instead of "go".
An adverbial superlative ("best") comes first.

Is í an Ghaeilge an teanga is fearr a labhraím.

So, is it correct to say that "a" is used for a direct relative clause and "go" for an indirect relative clause?
Also, just to stroke my ego a bit, would you consider this an intermediate level question or still a beginner question?

Although I initially thought it should be "Gaeilge" without an article, I can see why it would be "an Ghaeilge" with the article.
Any guidelines or suggestions or tips on figuring out when Gaeilge (and similar words) does an doesn't take the article?

No, not in Standard, Connacht or Ulster.
"A" is used for both, direct and indirect relatives. ("ar" in past tense indirect relative)

"Go" is used for indirect relative clauses only in Munster.




I don't know.
The problem is probably that "that" is used for both noun clauses and relative clauses in English.
("I know that ..." vs. "the language that ...")
Both "that"s are different.
In Irish the first is "go", the second "a".



Except for phrases as "(speaking) in Irish", "translate into Irish", "I can speak Irish" and perhaps a few others - it is always "an Ghaeilge".

Yes, but go is used only in Munster and is considered non-standard. In the C.O. it's a/arfor the ind. rel. too.



Somewhere between the two.?



With the article when referring to the language in a general sense - much the same as in French and Spanish, I suppose.
By the way, I don't think ach amháin is suitable for "except for" in this context. I'd say seachas an Bhéarla or diomaite den Bhéarla

So, to summarize, "Except for English, Irish is the language I speak best" would be

Seachas an Béarla, is í an Ghaeilge an teanga is fearr a labhraím.

Do I have that right?

Also, Labhras, thanks for pointing that it's usually "An Ghaeilge" more often than not. That thought never occurred to me before.

GRMA all

Thig leat "taobh amuigh don Bhéarla" a rá fosta.

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