My first attempt at making black bread. I used the recipe from Gerhard Kellner's website ketex.de. Google translate worked great at making it a useful recipe. The rest I used Hanseata's guide to German flour and US equivalents.
Having gone through this recipe now I would suggest the following -
1. Soak the old crumbs first and smash them throughly - I found the pieces absorbed too much water and let some out after smash.
2. Soak nuts in a shallower bowl - the nuts at the top of a higher bowl didn't absorb as much water.
3. I substituted 150g light rye (I had this on hand, not medium rye) + 50g whole grain rye. Next time I will use the 200g medium rye in the dough.
4. Kneading was a struggle, I waited sometime for dough to completely absorb the liquid but it was sticky!
5. Covered loaf pan helped not getting the bread too brown and gave me more oven time at lower temperature to reduce liquid.
Lastly, wait 24 hours before cutting. I noticed the bread was releasing a lot of moisture during cooling. And yes, I will definitely make this again!.