"Bruidhinn nas slaodaiche. Tha beagan Gàidhlig agam."
Translation:Speak slower. I have a little Gaelic.
"Tha beagan Gàidhlig agam" means "a little". To express "little" you would turn it into "chan eil ach beagan Gàidhlig agam" = "I don't have but a little Gaelic"*), or "chan eil mòran Gàidhlig agam" = "I don't have much Gaelic".
*) Note that for English "I have but [something]" Gaelic uses "I don't have but [something]. "Chan eil ach aon bhotal agam" - "I have but one bottle".
That's because it isn't quite right. nas slaodaiche is the comparative form, so you have to have it as a comparison, 'slower'. If you'd included 'more slowly' it might have worked. I have not checked. nas X = more X, as X = most X. Adverbial form is usually expressed using 'gu' 'gu slaodach' might be 'slowly'