Translation:The member is working in the hotel and at the restaurant.
"to work at the restaurant" has to be translated as "im Restaurant arbeiten" (not only as a physical place, but as a workplace). If it would be "We meet at the restaurant", it could also be "Wir treffen uns am Restaurant", if you don't intend to meet inside. It's just a different usage of the prepositions, there is not one-to-one correspondence between them.
British English would often say "work in the restaurant". The main point is that each language (and often, dialect) uses prepositions differently - and you have to remember the customs in the language you are learning, even though you would then translate in the way that is appropriate to your own language.
Languages don't translate verbatim.