Uh...medru? Surely "dach chi'n siarad Cymraeg?" is a valid answer....what is "medru"???
gallu and medru both mean 'being able to, to be able to'.
Dach/Dych chi'n siarad Cymraeg? means 'Are you speaking Welsh?' or 'Do you speak Welsh?'.
yes, dach chi'n siarad Cymraeg is correct too, apologies for medru appearing it's only there as an acceptable answer for users in North Wales. It's not in the list of taught words yet, something to add to the next version.