すみません、もう一度ゆっくり言ってください。

Excuse me, could you say that again more slowly?

すみません、もう一度(いちど)ゆっくり言(い)ってください。

Sumimasen, mōichido yukkuri itte kudasai.

済みません (すみません)

excuse me; pardon me; I'm sorry; thank you

もう一度 (もういちど)

once more; again

ゆっくり (ゆっくり)

slowly; at ease; restful

言う (いう、ゆう)

to say; to utter; to declare; to name; to call; to go (e.g. "the alarm went ping"); to make a noise

下さる (くださる)

to give; to confer; to bestow; to kindly do for one; to oblige; to favour; to favor

Readings: イチ、イツ、ひと-、ひと.つ

Meanings: one, one radical (no.1)

Readings: ド、ト、タク、たび、 -た.い

Meanings: degrees, occurrence, time, counter for occurrences, consider, attitude

Readings: ゲン、ゴン、い.う、こと

Meanings: say, word