hi...
First, was is not there a help chat in the site?

My question is, when i build a community lot, (and it does not belong to my sims) and then let a family go there, the game itself assigns the chef and employes in that lot, right?
If it has a restaurant, can i specify the food menu with custom food?

If that does't work..

Let's assume I let one of my sims buy that community lot and he assigned the menu, but he did not hire employes or chef, will the game assign employes when a family visits the lot??

If a community lot is not owned by a sim, then the game will automatically assign employees to fill the spots. Also, the menu options for a restaurant will be the default Maxis options. But if the community lot is owned by a sim, then all the positions will need to be hired/filled by whomever you choose. And then you can also select what food (Maxis or custom) that the restaurant menu will have available.