It only means 'have' in the sense of obtaining or receiving, or in this case consuming.
There is no equivalent to 'I have' as in English denoting possession.
We use the slightly longer phrase 'There is with me'
So 'I have a car' is transposed into 'There is a car with me' = (Mae car gyda fi)
There are lessons on this later on in the course.
Cael: Syncopated form of caffel, from Middle Welsh caffael, verbal noun from Proto-Celtic *kab- (compare Cornish kavos, Breton kavout), alteration of Proto-Indo-European *kh₂pi- ("to seize; to grab", compare Latin capiō, English have, heave, Albanian kap).
I wrote "I've already had breakfast " but the correction said "a breakfast ". Who says that?
The algorithm isn't intelligent, when it encounters a mistake it searches for the nearest accepted answer (there are 7 in this exercise the one quoted is not a common one).
Your suggestion would translate as:- dw i wedi cael brecwast eisoes (where eisoes = already)
Earlier in the course, we encountered "Dw i wedi cael bath heddiw", which if I recall correctly was " I have had my bath today" (or perhaps that was accepted but not a exact translation). So I took "cael" to mean something like "my" (my bath as opposed to a bath in general). So when I encountered this phrase I answered "I have had my breakfast". But this was not correct, or at least, not acceptable. I see below (rmcode's response) that it means "to have" in a way. OK, but is it only when I have something? In other words, could you say "Dych chi wedi cael brecwast" and it would be correct? Diolch.