In the meantime I found the solution:
Check in wordpress administration tool via tools => localization => WordPress.org thes terms: < Prev and this: Next >
and exchange them with your preffered terms.
Or the same, directly in this file:
wp-content/languages/de_DE.po
(while de_DE.po should be your language e.g. en_EN.po)
It works with me.
Sorry, I found this one, stupid – it’s just changing the border radius of the window in the options …
