Why we use here 'lenge' rather than 'langt'?
'lang/langt/lange' is describing the length of something.
'lenge' is describing the duration of something.
Ah, so that's why "Lenge" is "For a long time" in English. In Norwegian duration is part of the word, while in English it is not
But one can say "for long"
And a lengthy shower they had