Such a big diference between her speaking fast and slow. Sometimes I think that speaking fast she just ommits some of the words. May be it is because of my poor music skills, but here I didn't manage to hear "og" at all even after the 10th repeating. Is it normal for Norwegian or just a program's feature?
"En"(ei,et) when unstressed mean "a"/"an", and when stressed they mean "one". Some people prefer to write this pronunciation as "én"(éi, ett), but the language council of Norway approves of the spelling without the accent for both meanings. En/Ei/Et as separate words never mean "the", but the endings -en/-a/-et (which indeed look like the indefinite articles!) mean "the". So "en maur" = an ant, "én maur" = one ant, "mauren" = the ant. In reality the rules of when to use which articles and which forms are not completely one to one between English and Norwegian, but that's another discussion.