Astra G 2002 Sedan the car looks and feels more solid and stable, it is not soft but not hard either, something in between TOWARDS hard. Since there are no instructions and I was searching on the internet, the installation is as follows.

Front:
From the stock ones you take the top mount and together with the top mount from below there is a plastic piece that has the bearing clipped in (that's what I call it, it's like a ring that has balls inside) you need the Top mount and that ring you place on top of the coilover struts, the ring (it doesn't clip anywhere like the stock ones) and on top of the ring you press the top mount and screw the nut and it's ready to be installed on the car, then you adjust the height as you wish with the tool that comes with it.

Rear:
You remove the stock ones and the car from above has "rubbers," you remove the top one, it goes to the bottom, and you place the bottom one on top unless in your case the top rubber is different and you can place the springs without removing it, then you can simply cut the inner edges a bit from the bottom rubber so that the part you adjust the height with fits well, which you place from the bottom side of the spring (the spring has one side that is flat, that one rests against the part you adjust the height with).

I hope I helped those looking to purchase.