This site has native speakers pronounce words: http://www.forvo.com/search/mannen%20drikker%20vann/
That's Danish pronunciation. Click that Forvo link, type drikker in the search bar and then compare Norwegian and Danish pronunciations.
There is only one present tense in Norwegian which can be translated, depending on the context, as Present Simple or Present Continuous in English.
The man drinks water is correct as well. No, it can mean both habitually and at this very moment but the translation depends on the context.
Adverbs can be of great help. For instance, Mannen drikker vann hver dag translates to The man drinks water every day.
It's n (alveolar nasal consonant, [tongue touches the bone just behind your teeth]) because you don't bring your lips closer together to make an m sound (bilabial nasal consonant [closed lips suddenly open]).
Maybe since they are both nasal sounds, you get the impression that it's m instead of n.