- "Znüni" and "Zvieri" are the mid-morning and mid-afternoon brakes one takes. "Znüni" has the number 9 in the word, and "Zvieri" the number 4 - the average time when the brake from work is taken, and one has a small meal. If you work in an office it's maybe something small like a piece of fruit or Gipfeli (Croissant) and coffee/tea. Farmers and laborers may eat a hearty meal to gather strength for their hard work. It's common in every part of Switzerland.
Bauernsuppe (Buuresuppe, Puräsuppä) is a soup consisting of dried meat, vegetables/onions bouillon topped with a little cheese.
The soup can differ from town to town, from Kanton to Kanton – actually even from household to household. It depends on what one has in the pantry some add a little milk to it, some a bit of barley or beans.
- Rösti = hash brown
- Güggeli = literally "small rooster". It's a roasted chicken, also called "Mischtkratzerli" (literally "manure scratcher")
You can eat them all over Switzerland, and there is no city better than an other. It may differ from restaurant to restaurant or Güggeli roaser to Güggeli roaster ;)
- Of course we understand Hochdeutsch - it's the language we read and write. We never would expect tourists to speak Schwiizerttüsch (Swiss German), heck, sometimes we don't even understand each other :) I wrote a little about it at my blog:
Hope that answers your questions.