The following applies to Zurich.
Yoghurt:
-Plastic container: If it says PET on the bottom (which it probably doesn't), then recycle it with your normal plastics at the grocery store. If it isn't PET, your grocery store might have some fancier plastic recycling options, but if it doesn't have a place for other plastics then you need to throw it away in your Zuri sack.
-Paper around cup: put it in with your cardboard recycling. If you tie your cardboard with twine, just put your smaller pieces of cardboard between other uniformly bigger pieces so that the whole stack has integrity when you tie it and put it on the street at that time of month.
-Plastic cover: This isn't PET. As with the container, if your grocery store is fancy you might find a recycling option there, but otherwise put it in the Zurisack. Good luck reading the German labels on the bins!
Potatochip packaging: Zurisack. Bigger grocery stores, like Migros at Lindenplatz, have a packaging disposal option. I'm not sure what they do with it or if it gets recycled, but I think you're supposed to use it before leaving the store for large plastic wrap and such, not to bring in bags of packaging from home after you've eaten your chips. If I'm wrong I hope someone will correct me.
Chocolate wrappers: those foil/plastic ones go in the trash. The fancy ones that come in thick paper and foil can have the paper recycled with your cardboard (all paper thicker than printer paper is considered cardboard). The foil part I throw away in the Zurisack because it isn't thick like tin cans, which go in the metal recycling, but maybe someone else knows a better way to dispose of it.
Ice-cream container: If you're talking about the black lidded, white plastic ones, these aren't PET, so unless you have a fancy grocery store plastic system, they go in the Zurisack.
Haha, yes, a course could have been useful. You can do a general orientation course through the city (for free?) where you can ask recycling questions. Go to city hall to get the pamphlet with the dates and signups if you don't already have the one they send all new-comers in the mail.
To reassure you, everything that goes into the Zurisack will get sorted again later by hand to be reused as efficiently as possible. Sure, there's a slight environmental impact to using more plastic Zurisacks throughout the year, but beyond that you're not hurting the environment by throwing away reusable plastics and packaging in the Zurisack. You're just paying for the privilege of not having to sort it yourself since not sorting causes you to buy more of those costly Zurisacks. So if doing it all perfectly immediately is too stressful, rest easy because it's really only your pocketbook, not the state of the environment, that is straining a bit when you don't sort perfectly. Using reusable bags at the grocery store and for produce will have a greater saving effect on the environment than the few Zurisacks you'll save per year by worrying over the last few types of waste that don't have accessible recycling points.