Rats…
Live by the sword, eat your own dog food, karma’s a…
I didn’t actually test my suggestion 
'exten = +49695880780272, verbose(1,[${EXTEN}@${CONTEXT}])'
should be:
'exten = +49695880780272,1, verbose(1,[${EXTEN}@${CONTEXT}])'
But…
I don’t see any DE language options in asterisk-17-current.tar.gz. I found DE files on https://www.asterisksounds.org. They seem to work – at least they say something I can’t understand 
Good luck.