In the third course, we have the sentence “They heard what we understood”
My reply: (phonetic) Cluonew baith oneen deall.
The reply, as I hear it given, is: Cluonew baith oneen E theall
I am wondering, am I hearing “They heard what we To understand”? If so, why?
Oh, sorry. I wanted to go to hear this but you forgot to be more specific. Is it still Gwers 18 or you’re any further. I can’t remember from my head just right now in which lesson this sentence was. If you can be more specific I could go and listen to it to establish if I hear the same as you do or not.
Diolch.
If this is Lesson 18, around 25:35, the prompt would’ve been
“They heard what I understood”, not what we understood.
The response you heard was indeed
“Clywon nhw beth o’n i’n ei ddeall”.
So, the last bit “…beth o’n i’n ei ddeall (e)” would translate to “…what it is I understood”
I had an explanation in my head just now, but I then questioned it and forgotten what I was actually questioning - meaning I need sleep!!! Hopefully someone will explain by the time I wake up in the morning when I’ve figured it out again (and give a better explanation than I can!).
Yes, sorry, it is lesson 18 on course 3. in the second half of the lesson. But I don’t know the exact time.
So, the “I” surrounds the " understand “ee ddeall e”? That would make sense to me.
I haven’t listened to the lesson, but basically what @faithless78 says.
“beth o’n i’n ei ddeall” (what I understood)
Or
“Beth o’n ni’n ei ddeall” (what we understood)
Basically, it’s one of those things where literall translation doesn’t work. Welsh uses “what we understood it” in a way that English doesn’t. I could start saying that a transitive verb in Welsh normally needs an object in such things, but that doesn’t really help matters. More logical than Engish, but different! Easiest to just say that is how Welsh works. 
Ah, or more literally, “what I/we it understood” Makes little sense in English but it is clear to me how the welsh works in translation, to say it that way.