would hard on its own be "yn galed"?
"Hard" as an adjective is caled and as an adverb yn galed.
Diolch yn fawr!
I must work hard or I have to work hard?
They're the same in Welsh.
i was taught i have to or i must for rhaid i fi so why when i translate the sentence as i have to work hard is it marked wrong?
That was my point. I didn't report it as a mistake, because I was unsure whether it would be considered bad English. If it comes up again I will report it.
i have just reported it as i agree with you on the translation