Everybody in norway owns a bear... didnt you know that??
Mhmm! that's why I'm going to Norway! :D
You mean this bloke here?
Indeed; that man there.
Bjørn is also a common boy's/man's name in Norway. You can literally call baptise your son "Bjørn".
How does one know whether it is et bjørn or en bjørn. It is the latter apparently but I don't know why or how I should know...
Memorization. You simply need to memorize which nouns have which word associated with them.
Would "Mannen har bjørnen" be wrong?
It means 'The man has THE bear'. So it would be wrong.