Proverbs' use in a text

[majus]

One short question.

Can I use proverbs like kill two birds with one stone in a written test? Or are they only used in conversations?

thank you for your answer(s)

[tanhuimei]

Both also can!

[mosaic]

I'd say you can use it in a written text although it depends a bit on what kind of a text you're referring to.