"Before the sales started."
Translation:Cyn i'r sêls ddechrau.
I can mean either, depending on the context. 'Cyn i'r sêls dechrau, es i adre' = 'Before the sales started, I went home'; 'Cyn i'r sêls dechrau, dw i'n mynd adre' = 'Before the sales start, I'm going home'
Thank you. I had seen a Welsh speaker write it without the soft mutation, and I wondered.
Mutations are fickle things in the wild - some can change according to formality, dialect, background of the speaker etc. The mutations taught here are fairly standard, so you're probably better learning the ones Duolingo introduces and then as you become more fluent you can learn when to drop them or use a different mutation.