could someone please explain why it's "gyda Dewi Lingo" instead of "arna Dewi Lingo"?
Not sure of the reason but it is correct for it to be "gyda Dewi lingo". I also noticed that you said "arna Dewi Lingo". This is wrong as the correct form of "ar" to use there is "ar Dewi Lingo", "arna" is used for the first person.
ok, thanks! I've since noticed the pattern that for sore body parts it's "gyda..." but for illness you have to use the suitable form of "ar".