I don't quite understand how this genitive feminine lark works just yet, but I'll persevere :)
The definite article is an for all singular nouns, with the exception of singular feminine genitive nouns, for which it’s na. (The definite article is na for plural nouns of both genders and all cases.)
Could someone please explain why things go into the genitive with the verbal noun? Is there a guideline or set of rules to make it easier to learn?
If you think of the very literal translation of ag labhairt as "at (the) speaking" then the use of the Tuiseal Ginideach becomes a little bit more obvious - I am at the speaking of Irish