Complex sentence: One of the escape helpers was Reinhard Furrer (the future astronaut) who waited with Christian Zobel and two other escape helpers on the East Berlin side, ready to direct fugitives to the tunnel's opening.
Split into simpler sentences: One of the escape helpers was Reinhard Furrer, the future astronaut. He waited with Christian Zobel and two other escape helpers on the East Berlin side, ready to direct fugitives to the tunnel's opening.