You're talking about http://en.wikipedia.org/wiki/Wolof_language#Example_phrases
As for how to divide the words, that Wikipedia article has the following:
Gambian Wolof has an <a> after word-ending doubled (i.e. geminated) consonants
The first syllable of words is stressed; long vowels are pronounced with more time, but are not automatically stressed, as they are in English.
Pronoun conjugation instead of verbal conjugation. In Wolof, verbs are unchangeable words which cannot be conjugated. To express different tenses or aspects of an action, the personal pronouns are conjugated - not the verbs. Therefore, the term temporal pronoun has become established for this part of speech.
In "Na nga def", "na" is glossed as "how", "nga" is glossed as "you-perfective", and "def" is glossed as "do". Don't know if that helps, really.