"Nach eil Frìseal gu dòigheil?"
Translation:Isn't Fraser really well?
I'm pretty sure this is correct english. You'd say I am well, fraser is well so I am really well, fraser is really well, so why not isn't fraser really well. I have to say I struggle to imagine a context in which you would use this but it is correct language wise as far as i'm aware
Yes, idiomatically it's peculiar, which is why it bothers people, but there's nothing wrong with the grammar. (You'd need a linguist to explain why it's wrong, not a grammar teacher.)
We're still learning the basics of Scottish Gaelic. So the English translations need to be quite close in meaning to the Gàidhlig, which means they will be awkward and clunky at times.
And we're dealing with translating adjectives, adverbs, and intensifiers, all of which in combination get really weird at times. Like, some you can combine in the positive sense only, some in the negative only... And there's no real correspondence between them from language to language.