how to allow connection to wifi (internet) but not home network

Hello guys,

I need some help to setup my network. Best way is to explain my situation so you can understand what exactly is going on!

I live in a building and have two separate small units located side by side. The are small and my wifi covers both apartments.
In the apartment I live I use my pc and my nvidia shield on a network and have my shared folders and drives from the PC.
I want to allow my guests and friends to have access to internet by connecting to the wifi. But I want to be sure that they
are not able to access my network (file and folders on my pc).

Is there a way to restrict network access by mac address or any other trick? If this is not possible I don't mind buying a
separate router (modem) for the other apartment. But that modem will also get internet from MY apartment.

Thanks for your replies. My router unfortunately only have a restricted access mode to block internet access on predefined
days or hours. But nothing concerning the private network access restriction.

Do you think I can buy a router for the other apartment, connect it to internet by (main routers wifi) and set it to block all
home network access?

Often you won't spot it but under security or wireless there may be an option user isolation of similar that's what blocks local lan

The router is a bbox Modèle TVW620.I. It is provided my my isp and connected to the fiber network. So I really don't know
how to change that! The only setting I have on this router is to block wifi connections at specific hours of day and week!