On the page itself it states:
The following instructions currently apply to NextGEN Gallery versions 1.19.13 (a.k.a. NextGEN Legacy) and before.
and
NextGEN Gallery (branch 2.0.x) will be updated with a complete i18n implementation in a soon to be released version.
We need German language for Version 2.0.40 . The page neither states which version of NextGEN will be translated it just says branch 2.0.x but we already use 2.0.40 and theer is no German language support.
cu Axel
.