In week 18 (Challenge 17), one sentence is “Did you enjoy that film at the weekend?” and the Welsh was “Nest ti joio’r ffilm 'na ar y penwythnos?”. So far, so good. But then the next sentence is “Yes, I enjoyed it very much”, and the Welsh was “Do, joio es i’n fawr iawn”.
I’m confused why the response to “Nest ti joio?” is “Joio es i”, rather than “Nes i joio”. What’s the construction, and what would the question/response be for “Did he/she enjoy?” “Did we enjoy?” and so on, please?
If I’ve listened to the right bit, the answer I heard was “Joiais i fe yn fawr iawn”. This is using the short-form preterite verb, but “nes i joio” means the same thing, it’s just using an auxiliary preterite instead. You can use whichever you prefer but it’s always worth being aware of the one you don’t usually use for when you hear other people use it.
‘yes’ responses to…
did he/she enjoy? = naeth e/hi joio / joiodd e/hi
did we enjoy? = naethon ni joio / joion ni
did they enjoy? = naethon nhw joio / joion nhw
Ohhhh right! “Joiais i” and all the others make sense now - that’s the problem between listening and reading 
Many thanks, Siaron.