Yes, you heard correctly.
Now, for the why… well, colloquially, you’ll hear Well i ti fynd for You’d better leave, and as a sentence/command on its own this is fine. But the complete structure is
Byddai’n well i ti fynd, literally It would be better for you if you went, and in a subclause or reported speech, the shortened form just doesn’t work.
Not related but can’t figure out how to add a new comment from my phone 
Would you say the most accurate translation of efelychu is to recreate? My somewhat older dictionary says imitate, but most results on bbc are sports related and along the lines of recreating or repeating a past success.
I could see how imitate might be used in this way, but it doesn’t work the other way around as in “stop imitating (recreating) me.”
Diolch yn fawr!
efelychu is to imitate or to emulate, so I think the sports comments are probably using it in its ‘emulate’ capacity, and that ‘recreate’ is just a synonym that could be swapped in in certain contexts but wouldn’t be suitable in other contexts.
Helo, first the challenge explains that “am” is followed by a softening, but then it is “am tua mis” and not *am dua mis. Why is that? Which words soften after “am” and which don’t?
I can’t really give you a reason here, but some words are just never mutated, tua being one of them. Another example I can think of off the top of my head is am byth (= forever).
Don’t worry too much about this, you’ll learn those exceptions by being exposed to them, and even if you make mistakes in mutation, people will still understand you.
Yeah as @Hendrik says, mistakes in mutations in most circumstances don’t matter because they don’t affect the meaning and therefore understanding.
With “ei…fo” and “ei…hi” the mutation in the middle is more important because it can affect meaning especially if the following fo/hi is dropped. But please don’t worry about this.
Thank you, Hendrik. This makes sense. I hadn’t equated “you had better….” with “it would be better for you…”.
Just Realised that ymarfer - (practice) and arfer - (custom/accustom) are similar 
…
Yes they remind me of the many meanings of the English word “Use”
Is there an equivalent of the English term/phrase … “dark horse” ?? (someone who has hidden talents or skill)
Yes, it’s " 'deryn y nos" - in Welsh it’s ‘night bird’ rather than ‘dark horse’ 
Diolch.
Is it spelt deryn even in formal writing or aderyn?
I learnt “tipyn o deryn” in my family… as “cock of the walk” (bit of a lad)
I guess it would be aderyn in formal writing (unless it was poetry that needed only two syllables in order to scan or cynghanu)
As Siaron said, the official spelling is aderyn, and this kind of “dropping the first vowel” happens quite a bit in speech. Some examples are ystafell -> stafell, Eisteddfod -> 'Steddfod. And the command form of eistedd (to sit) is also often heard as 'stedda/'steddwch
Hello!
At 18:07 on challenge 07 (level 1 south) the narrator says “You said you’ve been learning for about a month”.
I thought this would be translated to “Dwedest ti ti wedi bod yn dysgu am biti mis” but apparently instead, it’s “Dwedest ti bo 'ti wedi bod yn dysgu am biti mis”
Is this something to do with there being two consecutive ti’s after one another? Since doesn’t the narrator’s translation actually translate to “You said that you’ve been learning for about a month”? There was no mention of “that” in the english sentence whatsoever.
Sorry, really nit-picking here but it’s small changes like this I hope to turn into second nature if this is indeed a grammar rule. Diolch eto!
It’s because while ‘that’ can be (and often is) inferred in English, it can’t be inferred in Welsh - it has to be there.
Ahh I see. Diolch 
I’ve noticed with these courses that ‘pub’ is the same in Welsh except for the awkward spelling. Its an shortening for ‘Public house’
My family used to say ‘tafarn’ … ‘ hel tafarnau’ (pub crawling) I heard… so when did that change happened? My family was northern Ceredigion
Or is it just a Gwynedd town thing? Ive noticed Cofis/bethesda using total different vocab so can be confusing. I’m learning northern dialect mainly because my family used northern dialect between Aberystwyth and Machynlleth…But they can impressively understand and switch to Northern Carmarthenshire and southern ceredigion lingo driving some mad 
Hi @brynle
The southern course uses tafarn. To be honest I think the southern course goes up to Aberystwyth on the western side …after that it’s definitely ‘North’!
Its impossible to draw a line of course because it doesn’t work like that - with particular things said in particular regions a short distance apart - and of course people will understand / underlyingly it’s substantially the same either way.
Rich
In the old North course ‘pub’ is used, but in the new North course its ‘dafarn’