"Very good. I have a little Gaelic."
Translation:Glè mhath. Tha beagan Gàidhlig agam.
You don't know because they haven't told you and they haven't told you because nobody knows. Some languages (like English) put adjectives before the noun. Some (like Spanish) put them after. And some (like Gaelic, Welsh and French) put most after and a few specific common ones before. How this came about is unknown, but it is often the same ones. For example Gaelic seann, Welsh hen and French vieux all mean 'old' and all go before the noun. If you are having trouble sleeping you could try this to cure your insomnia.
However, something else is going on with beagan. It is not an adjective but a noun. The word little is confusing, but you can tell which it is because if it is an adjective you can replace it with small or wee, which would be beag and go after the noun. But that doesn't work here. So this shows that beagan is different - it means 'a little bit' so beagan Gàidhlig means 'a little bit [of] Gaelic'. D