I got the problem that I cannot change the message shown in the box. Even though I changed the message in the file:
'Root/typo3conf/ext/cookieconsent2/Resources/Private/Language/de.locallang.xlf'
I first thought there could be another file but I were not able to find any other and my next guess was maybe a problem with the cache. But this did not work either.
I appreciate any help!
The Messages of the translationfiles are cached, so if you changed something in these files you've to delete the cache in the backend (administration-interface) of TYPO3.
Furthermore perhaps you edited the wrong file. The file you posted is for German language and to display that you've to have or create a setup for the German language. The English files never have the prefix "de." or any other prefix.