German updates needed for W3C i18n articles

The English original has been changed for a number of articles, and the 
German translation needs to be updated to follow.  Some updates are just 
a sentence or two.  The translation tracker issues below indicate what 
changes are needed.

https://github.com/w3c/i18n-translations/issues/24

https://github.com/w3c/i18n-translations/issues/30

https://github.com/w3c/i18n-translations/issues/40

https://github.com/w3c/i18n-translations/issues/45


I'd be grateful if Gunnar or someone else can offer the needed 
translation text.  Where there is only a sentence or so, the 
translations can be sent as text in email, if preferred. GitHub pull 
requests also work.

thanks in advance,
ri