Translation language not correkt

[TildBJ]

Translation does not work properly when translating a normal text field.
Sourcelanguage is german in my case and target language should be english.
After translation the text i got from deepL is french...

Small debug output, maybe it helps:

PITS\Deepl\Service\DeeplService: 108
array(5 items)
   auth_key => 'secret' (36 chars)
   text => 'Deutscher Text, der übersetzt werden soll' (42 chars)
   source_lang => 'EN' (2 chars)
   target_lang => 'en' (2 chars)
   tag_handling => 'xml' (3 chars)