Then I made a copy of default.mo & default.po that can be found under /lang in the Sentence-folder, and renamed them to match my language (sv_SE). If you want the blog in German then you need to rename the files to de_DE.mo & de_DE.po.
After that I opened the .po-file in poEdit (the icon has changed to a terrestrial globe).
When you have that file open, you can translate all the keywords that you would like.
When you have translated all the wanted keywords, upload both your de_DE.po & de_DE.mo files into the folder /lang in Sentence on your webserver.
Hopefully this will work. In order for this to work you need to have German installed as your main language in the WordPress Dashboard.