An unusually large amount of limescale has settled on the bottom of the water container.
Check the set water hardness level and set the level that applies to your tap water.
You can determine the water hardness level for your water using the test strip provided or by asking your local water authority. Water hardness is expressed in water hardness levels (I to IV) or in German hardness grades 1 to >22 gpg (1 to >21 °dH).
Descale the appliance as described in the operating instructions.
