"Mae Ceri Lingo yn gyflym mewn ras."

Translation: Ceri Lingo is fast in a race.

[NicDafis]

Suggested Ceri Lingo is quick in a race as an alternative.

[PushythePirate1]

I put Ceri Lingo's fast in a race, which was marked wrong.

[Sir_Percival]

How about, 'Mae Ceri Lingo'n gyflym mewn ras'?