“Can I ……?” / “May I …….?” is “Ga i ……?” and the word following takes a soft mutation but for “Can I/May I have…”, you don’t need the ‘have’ - it’s built in to the ‘ga’ because that itself comes from cael.
So for your examples -
Can I have (a cup of tea) = Ga I (banad o de)
Can I do (something for you) = Ga I (wneud rhywbeth amdanat ti)
Can I buy (that book) = Ga I brynu (y llyfr yna)
etc - e.g. Can I close the door/open the window = Ga I gau’r drws/agor y ffenest
a quick one that I thought about while hitting the snooze button on this very wet and unmotivating day:
We say something like: “fyffa’i byth…” for “I will never…”
Can I extend this to: “dw i wedi byth…” for “I have never” Or “dw i wedi wastad …” for “I have always wanted” or “dw i wedi wir moyn” for "I have really wanted… " etc
Basically I am trying to add a bit more the “dw i wedi bod yn…” structure we have learned and the above is what seems sort of correct…thanks!
It’s great that you’re trying to extend structures you’ve learnt, so don’t stop doing that, but you happen to have picked one to work on that isn’t as straightforward as it first seems. Don’t worry though, things will click into place as you come across more examples of useage.
You’re kind of on the right lines, but when you extend ‘dw i wedi’ sentences, those 3 words don’t necessarily stay in that order. e.g. I have always wanted = dw i wastad wedi moyn, I have really wanted = dw i wir wedi moyn
However, when it comes to “I have never”, you need ‘erioed’ for the ‘never’ rather than ‘byth’… dwi erioed wedi