"I am going to chapel Sunday."
Translation:Dw i'n mynd i'r capel ddydd Sul.
The correction places 'r before capel but the is not in the English sentence?
'the' is not needed in the English, but 'r is needed in the Welsh.
yr/y/'r is always used with places that we go to regularly, especially if there is usually only one of them:
- Dw i'n mynd i'r gwely - I am going to bed
- Maen nhw'n mynd i'r ysgol - They go to school
More examples in the course notes for this section.