Hi there and welcome from a South African in Switzerland! There are quite a few South Africans on this forum and living here. It's possible some of them will be along with some advice soon.

Regards your questions I can only really help with one. It is extremely cold right now. I wear three layers when going out, sometimes four. My scarf, hat and gloves are going everywhere as well. A heavy coat, preferably a windbreaker, is a must. I like wearing boots that cover the ankles, it's common to see women wearing knee length boots at the moment. Imagine the South African winter, except the temperature in a South African winter at 5:30 in the morning is the maximum temperature here during the day and you might get an idea of how cold it is. Your initial dillema is this: what do you wear to the airport in South Africa with the temperature at +30° and still have enough clothing with you to wear when you get over here and the temperature is 0°?

Best of luck for your interview.