Care to translate for us non German speakers? Google makes a right mess of it....
...and my English is too bad.
But very important is at installing the rear suspension (no 16 in this photo report) the fact , that a lot of people are fixing everything at the rearssuspension , while the wheels and the suspension hanging loose down, which is definetely wrong because than you have the problem that you have tension at the bushes, pistonrod + seals when the car gets back on the ground. And the result is a much too firm ride + not enough lowering at the rear. So it is important not to fix everything tight untill the weight of the car is "damping down" the suspension.
The author at the report ( a Bilstein Suspension Expert ) describes the ride / setup of the combination of these Eibach Sportline springs a "much more agil and more sporty but without loosing much comfort.."
In general , donĀ“t forget that with the GTI suspension you have to reduce the Eibach lowering data by the approx 20mm of the GTI works lowering.