Friedrich Wilhelm Krummacher is regarded as one of the most influental 19th century preachers. Just this week I discovered his passion devotional on Vyrso: https://vyrso.com/product/40380/suffering-saviour
The German website www.glaubensstimme.de ("voice of faith") specializes in public domain resources - often with a reformed/evangelical bent - and hosts lots of his material. I put two very central sermons into a PB, see over at the German language forum: https://community.logos.com/forums/t/101182.aspx
- Die Rechtfertigung durch Glauben (Justification by Faith, sermon on Rm 3)
- Die Wiedergeburt (Rebirth / Becoming Born Again, sermon on John 3)
The PB uses sermon support syntax to achieve one book with automated index from several (here: two) sermons. For those who want to train their "theological German" but don't use German UI and don't get the instructions: just make sure to put the docx-files into the right sequence and build the PB as a monograph in German language for the bible text references.