I found it:
The text “get directions” sits in the file “mappress-google-maps-for-wordpress.pot/mappress-google-maps-for-wordpress.pot”
and the language – specific files are not synchron with the .pot – file!
it seems to me that the language specific files are for the free version and the .pot file is for the pro-version
So I have to synchronize the actual .po-file with the .pot-file and then translate the file and then take care that these files are not overwritten by the next update
it’s not a happy situation