Yellow PS fluid sounds like aftermarket PS fluid... regular PS fluid is clear, yellow color... Not sure what you have in yours at this point.
Amsoil says your car uses ATF and they recommends their synthetic ATF.
AutohausAZ says CHF 11S only if your car specifies it...
You can still buy 7.1... or you can buy alternative Febi Green... which is cheaper than Pentosin...
GermanAutoParts.com
I would just put in Febi Green or 7.1... not 11S or ATF...
You really have to suck out all fluids... You should consider changing or condition your PS hose at the reservoir before pouring new fluid in... at least one hose should be changed... and that hose has no fitting... goes from reservoir to another pipe. This is the hose that leaks 90% of the time. Other hoses that has special fittings... just trim the end of the hose off and clamp on new part of hose. Should be enough room.