I'd say so! "Dwi yn gwerthu" = "I am selling".. but if we're talking about the shoes being sold here, then I suppose "I sell" flows a bit better..
I know what you mean but "I am selling" would work too. It's nearly definitely just an oversight as the course has literally just been released into beta.
Yup, I agreed it should be accepted :D That's what beta's good for I suppose, hopefully they'll add it as an acceptable answer eventually!