Please use the "report a problem" feature to bring this to the attention of the course maintainers - I believe they don't read every sentence discussion.

Actually I'm not sure that "Rydw i'n Casnewydd" means anything! A sentence of that sort needs a verb-noun after the 'n, e.g. (Ry)dw i'n casáu Casnewydd -- I hate Newport. "I'm in Newport" would be "(Ry)dw i yng Nghasnewydd".