Hi you all!!

I'm a new member here and I have some questions that need answers. I've searched for a similar questions and knowledge about this for more than a month now, but I have yet found the actual answer for the situation that I'm currently in. Sorry for my bad English as I'm Thai. Here are the things:

I've owned Volvo S60 DRIVe 1.6 180HP 2013 for about 2 years now and it has around 34000 km on it. It has 18" R-design wheels on it (235/40/18). I recently upgraded the springs to the Heico ones without upgrading the shock absorbers. It has been around almost a month now since the upgrade. I noticed the ride has been harsher, crashier, and bouncier as well as I live in Thailand and there are enough bad roads, road undulations, rough concretes, etc.. My dad's C300 AMG has stiffer suspension but rides much more smooth than mine. This setup works well when the road is almost perfectly smooth. I should say that the handling and comfort are worse now. The only advantage of the spring is how it looks . When I drive on the highway, the car seems to go up and down all the time, and when rough road comes, the car vibrates and crashes as hell. I thought Heico springs were not as stiff and were as soft as the originals. I would like to have more floating ride (if you know that i mean), less bouncy, less crashy, more sticky to the road :roll eyes:. It should be noted that before the upgrade, the car felt more stable, more comfort, but it was less stable, less floating, and less sticky to the road compared to my dad's C300 AMG. After the Heico spring upgrade, it was a mess now.

So my question is this:
1) What is the original springs rate for my car?
2) Are the Heico springs stiffer than the originals?
3) I heard that Heico springs are basically Eibach, is this true?
4) Will upgrading the shocks make the ride better? And should I upgrade them? (e.g., Billstein B8)

Thank you very much for your answers and sorry for my bad English