"The waiters work in the restaurant."
Translation:Servitørene jobber i restauranten.
Yes, but it would be better to use the indefinite with 'på' in that case: "på restaurant".
Keep in mind that 'i' is still the preferred sentence here, and 'i' and 'på' aren't usually interchangeable.
Does it work, like in English, that på means place more of in a form ofan institution or a concept and i just a place? Like you can be at school even if it's a third world under a bridge and in school meaning in a school building? (my English told me that teaching prepositions in English, sorry if it doesn't make much sense)