Good evening,
we had a craftsman here. He also did a very good job. Somehow he cut into the tiles at the joints, then gently loosened them from the wall. That’s how he got to the cistern, where a new technology (das Hebelzeug dadrin) was installed. The tiles could also be freed a bit from the old plaster on the back, and after some of the wall was removed, the tiles could be cleanly reattached. He mixed the color for the joints and now you can hardly see anything. It took a very long time, but the price was less than we thought or if we had to have the whole wall redone with new tiles. All’s well that ends well.
Senni