"No it is not Dewi Lingo's fault, but yours!"
Translation:Nage, dim ar Dewi Lingo mae'r bai, ond arnat ti!
Yes, it's a very Celtic kind of expression using prepositions to express things. Dal ati gyda'r ymarfer / Keep practising!
I think the difficulty for many of us here is not the prepositions, but rather the emphatic word order. I found that the most difficult thing about the Irish program, and I am terribly grateful that there is either less of it in Welsh or you are being somewhat more merciful to us than they are.
I'm not sure how exactly it compares to Irish, but Welsh does employ the emphatic word order quite a lot, as does the English of certain parts of Wales (which makes Welsh more natural for those learners!). A good way to think of the pattern is "It's ... that ...", so here "It's Dewi Lingo that's to blame".
One of the biggest problems for native English Welsh learners, especially when speaking, seems to be to get them to remember to put the verb at the front of the sentence. Then when you ask them to switch it around, it all becomes a little too much for some!
Nage is the word for "no" when you're replying to a question or statement that isn't started with a verb. Usually sentences in Welsh start with a verb but you can put another part of the sentence at the front for emphasis sometimes:
Ar Dewi mae'r bai? Nage
lit. "On Dewi is the blame? No"
i.e. "Is Dewi to blame? No"
Or another example:
Yfory mae'r parti? Nage
lit. "Tomorrow is the party? No"
i.e. "Is the party tomorrow? No"
The "yes" for such emphatic questions is ie:
Yn y bath mae Siôn? Ie
lit. "In the bath is Siôn? Yes"
i.e. "Is Siôn in the bath? Yes"
Just to add for completeness: Or Naci for No and Ia for Yes, if you are learning Northern Welsh :)