It´s about this, right?
First of all, you need a "new" lever. The Iltis one has only 3 steps. Off, first and second speed. You need one from e.g. Golf1 or Jetta. They had that intermittent wiping contact extra.
(That´s what the first chapter said).
Next is, you have to built in the "Intervall-relay" into the existing wiring.
They decided to use the connecting points of the "Schalttafelkabelbaums" (switch board wiring), of the "Maschinenkabelbaum" (engine wiring) and that wiper motor.
You only need that wiring to the "Maschinekabelbaum" if do you want to use that combined wash/sprinkle relay. You also have to add another contact into the plug connector of the wiper lever in that case so you can keep the original wiring.
Next is a list of parts you need.
Now make that wiring as shown:
An connect it to the existing wiring and plugs. Only wiring No 53 need to be cut apart and if need be looped through the relay.
I didn´t even understand that German so don´t be confused about the translation.