"The education of the citizens is an important investment for the country."

Translation: Uddannelsen af borgerne er en vigtig investering for landet.

[mejdanek]

is it wrong to say "borgernes uddannelsen" instead of "uddannelsen af borgerne"?

[mads-elh]

Yes, but only because a noun after a genitive noun only takes the indefinite form, so you'd say "borgernes uddannelse". I've added "borgernes uddannelse" as a valid translation now :)