Translation:Dw i'n dost gyda'r ffliw.
Why is "tost" mutated here?
tost is an adjective. If it is not clear from the course notes why that mutates here, see - https://www.duolingo.com/comment/13844144
Why "gyda'r ffliw" is correct whereas "efo'r ffliw" is not?
They are both OK. The answers have now been amended. Thank you.