A little more detail:

There are moments in both comfort and intimacy in which Manfried speaks to Aviva in German, which she understands; things he only says to her.

For these moments, I'm only writing in the script that this dialogue is ad-libbed, as I prefer for it to be determined by the actors to know what would be said between them. It would not be translated into subtitles, as only they would know. It's something that I think would help keep up the much needed intimacy between the characters.