"Ni" as formal singular is not old-fashioned, but a misunderstanding made by several younger people in Sweden. It was rather used to mark class differences and create distance between people and we have worked hard to get rid of it.
In the 1960s and 70s there was a "du-reform" in Sweden where all people started to say "du" to each other to improve equality in society. Recently, influence from other European languages has made young Swedes believe that "ni" was used in the same way as "vous" in French or "Sie" in German, but the emotions for "ni" have never really been quite the same.
You should not try to use "ni" as formal you since many older people in Sweden may feel offended.
Could you help me?
Where can I looking for words? For example, what you wrote. "brev"-/bre:v/
I would like to see all of the words, what I learnt here :)
Update: I found this: http://lexin.nada.kth.se/lexin/#searchinfo=both,swe_swe,man; I understand only one thing... How I write a word when I try to speak... It is enough to me:)