Shwmae. As an English only speaking Welshman (head held in shame...) Dewi is a common first name but is not translated into David by English only speakers in Wales. It is also common for English only speaking Welsh to have wholly Welsh names. E.g. Sion for John.
Looking forward to brushing up on my long out of use Welsh here though. Can't wait until we get to the various mutations!
Pob hywl ac pob lwc (I think)
If you read the lesson more carefully, it will be obvious which form the answer needs to be in. If it's "type what you hear" or if it wants you to speak, then of course it will need to be in Welsh. If it wants you to type the translation, then it will depend on whether what they give you is in Welsh or English.