Dydh da! @KarmenKern
Apologies for the slow reply! The Go Cornish course was created by another user and not by any of our in-house linguists - sadly none of us actually speak Cornish. The creator of the course has left an email address in the course description though so that you can contact them - email@example.com
They will definitely have a better idea of the difference between “gwag ov vy” and “yma nown dhymm”. I don’t speak Cornish, but I’ll give you my best guess as a linguist. It looks like “gwag ov vy” literally means “I am hungry (or empty)”, so the structure of the sentence is pretty much like English (gwag=empty/hungry; …ov vy=I am…). But “yma nown dhymm” looks more like it’s literally saying “I have hunger”, or even more literally “there-is hunger to-me”. This is a common way to talk about hunger in many languages (especially in other European languages like “j’ai faim” in French, “ich habe Hunger” in German).
As for when to use one over the other, if they’re both in the course, then it’s likely that they’re both in common usage. One possible reason why there might be two versions is that “gwag ov vy” is similar to English, and since nearly all Cornish speakers also speak English, this might have crept in due to influence from English, and “yma nown dhymm” might be a much older Cornish form. Of course, all of this is just a guess, so please do get in touch with Go Cornish for what I’m sure will be a much more reliable answer than mine!
As for the translations and picking the correct options, I suggest trying to remember that “gwag” means “empty” as well as “hungry” (one way to try to remember that would be to picture a duck discovering that somebody has stolen all the jewellery from its, now EMPTY, jewellery box, panics and starts shouting “GWAG GWAAAG!” - it sounds silly, but it will get the word to stick). On the other hand, “nown” only ever means “hunger”, so “yma nown dhymm” can never mean “I’m empty”.
I hope this helps! At Memrise, we always love to see people learning minority languages and keeping them alive, so please do stick with it and don’t hesitate to get in touch with anything else we can help with.
Omlowenha dyski (happy learning)!