I think this should go in the quick questions for quick answers section but I can’t for the life of me fnd out how to post there, so I hope posting my question here is OK
if “wnei di” means “you are going to do”
does “wnei fi” mean “I am going to do”?
and “wnei fo/hi” mean “he/she is going to”?
and wnei ni, wnei chi and wnei nhw etc
No, they all come from the verb gwneud but they have different forms depending on the pronoun:
wna i
wnei di
wnaiff e/o/hi but also wneith e/o/hi
wnan ni
wnewch chi
wnân nhw
brilliant, thank you Siaron
so will the mynd version go?
ges i
gest ti already realised this wont follow ha! oh well
gaiff o/hi
gain ni
gaiwch chi
gain nhw (with a torbach on the a, my keyboard cant do them atm)
i think Im getting my mynd all muddled with cael sorry!
No, because gwneud, cael and mynd are all irregular so they all have their little quirks!
Mynd -
Af i
Ei di
Aiff e/o/hi but also Eith e/o/hi
Awn ni
Ewch chi
Ân nhw
Cael -
Ca i (or caf i)
Cei di
Caiff e/o/hi but also Ceith e/o/hi
Cawn ni
Cewch chi
Cân nhw
thanks siaron
I have seen gaiff as opposed to caiff are they the same ? Is one a postive and anther negative or am completely barking up the wrong tree?
Not barking up the wrong tree, but it’s not as black and white as that!
caiff is positive and will mutate to gaiff if it’s a question, or when it follows the positive particles fe or mi (e.g. mi gaiff hi / fe gaiff hi), but also in a positive statement where the speaker has left out the positive particles (which is perfectly normal!)
Technically, caiff will mutate to chaiff in the negative, though in speech it often doesn’t.
I think my brain has just exploded haha ok I’m not going master this today but I am thinking it is a little bit like bydd and how that mutates to fydd as a negative and if the mi is used in front of it.
Thanks Siaron.
yup, exactly like bydd. But don’t get bogged down with it - if you mis-mutate it really isn’t the end of the world. The more you hear the patterns, the more your brain will absorb them naturally. It’s normal to worry about getting them right, but pausing to remember the rules (which are often very flexible in speech anyway) can do more harm than good when it comes to practising conversation 
Thank you Siaron, that’s advice that makes my brain hurt a little less 
how would one go about answering a request using the “wnei di (rywbeth)?” format, tybed?
dw i’n amau byddai hi’n debyg i glywed rhywbeth fel “ie”, ond just tybio. diolch!
If you want to be grammatically correct, you can answer either (Mi) wna i or Gwnaf. But I guess you could get away with ie. 