"I was there for more than a week I believe."

Translation: Bues i 'na am fwy o wythnos dw i'n credu.

[Steviebabes]

Shouldn't "more than" translate as "mwy na" because "mwy o" means "more of"?

[ibisc]

This sentence is another zombie, probly deleted becsuse of the mistake.

Yes, am fwy nag wythnos would be fine.