"bekommen" oder "werden"

Decide which verb best translates the predicate of each sentence, "bekommen" or "werden."
It's getting dark.
You've been getting a lot of mail.
You've been getting so tired.
It's becoming more expensive.
What do you want to become?
What do you want to receive?
They always get money for their birthday.
They become excited on their birthday.
You're getting a fever.
You're getting warmer.