"Kelner pracuje w restauracji."

Translation: The waiter works in the restaurant.

[Helcia3]

I feel like server should be accepted too. It is more rare than waiter, but it works fine.

[Jellei]

True, added.

[XanderStainton]

Why doesn't "The waiter work at the restaurant." work as well?

[Jellei]

Added "at".