thanks for your input...
1.) solution with "deactivate Synchronisation" worked for the content module, not for related products. Also not clear for me, why instances change on a module that's deactivated?
2.) I have products that sell for 7,50, that's including Spice and Spiceshaker. If somebody wants only the spice (without the Spiceshaker) i have a discount of 1,90 (so the Spice costs 5,60) . May be you could help me to find the best way to solve this with Hikashop
3.) issue - thanks.. i am sure that will work.