"Halò, tha Gàidhlig agam."
Translation:Hello, I have Gaelic.
In some parts of Scotland, chiefly those where some Gaelic speakers can still be found, because their variant of English has a lot of Gaelicisms in it. It's by no means standard, even in Scotland, I assure you. Despite that, I have no doubt you'd be understood, of course. It's simply that most English speakers (and it is supposed to be translated into English, not a specific and somewhat peculiar variety thereof) will not say anything like that; they'll say "I know" or "I speak".