DavecUK thanks for your answer!
I’ve double checked all connections and they are correct. Now I’ve set in the settings the fill level to low and then the pump started. Then I’ve switched the boiler heater back to on and it works. After pulling some hot water and steam even the refill worked. Now I’ve switched back to the standard fill level and it still works. I can’t understand but happy that it works!
I only have now one point where some water drips (hard to explain it in English for me-it is where the thicker pipe connected to the valve for the pump and on the other side connected to the overflow of the steam boiler and to the front). But at first I have to wait till the machine is cool again.