Winfriede has locked ben into the cage with the electronic code.
How to get it?
Anna can't see it behind that painting she is using for hiding.
Look at the painting next to the cage under the garment. The actual painting can be removed from the frame. You could do some spy-level stuff to it.
Cut eye holes into the painting.
Take it to kitchen and use the knife on the painting.
Put the adjusted painting back to the frame. Now you can move through the gace door.