1/ Schools are veritable Petri dishes. You WILL get a stinking cold at some point in the first term - it’s standard. You DO NOT, however, have to lose your voice. This will only happen if you don’t take care of yourself...
DO NOT talk over students. Wait for silence. There should be a way to combat low level disruption in your school behaviour policy, so make sure you are being consistent with your colleagues.
For a sore throat - keep yourself hydrated, take paracetamol, hot drinks with honey, and have early nights.
Remember - your job is not to achieve perfection. It doesn’t exist. Your job is to be a teacher - to do what you can - not to be a martyr to a card sort or data drop.
Also, your job DOES NOT DEFINE YOU.