"There is nothing the matter with you."
Translation:Does dim byd yn bod arnat ti.
It would be a lot easier to learn the words in an idiomatic phrase like this, if there were some way to figure out what each meant independently.
Doesn't hovering over them / pressing on them give you a list of hints that help suggest the meaning?
For example, I see that byd has the hints "world" and "anything" (along with phrase hints "there is nothing" and "nothing" for does dim byd).
So I'd venture something along the lines of "There-is not anything [verbal marker] to-be on you".
So I suppose yn here is a bit like a relative conjunction: There is not anything that is on you.