"I am going to the chapel Sunday."
Translation:Dw i'n mynd i'r capel dydd Sul.
It means 'On Sunday', but it should not have appeared that early in the couse to avoid confusion. Hopefully I've altered things now so it'll only appear later in the course. It's better to stick to the days of the week introduced early in the course, ie 'dydd etc.
How incredibly quickly you acted - congratulations! That is a far cry from the Italian DL course, where difficulties and errors are pointed out repeatedly by many learners, but never acted on.