I don’t understand

I am not a native English speaker.
So there are lots of questions, I can’t answer.
For example, the word ‘scent’
which letter, S or C, is silent?

Why is the letter ‘W’ in English
called double U not double V? What do I miss?
Why isn’t a fireman called a waterman?
This one I also don’t understand.

If a vegetarian eats vegetable,
then should humanitarian eat people?
How come noses run and feet smell?
Do you know the reason? Can you please tell?

Why do we call it a TV set
when there is only one? I don’t really get.
If money doesn’t grow on trees,
how come banks have branches? You tell me.