Accessing shared resource stored on local computer from different location

The main requirements for this task is to setup something in offices located on different locations, so (**1st question**) users are able to log on to the domain without VPN when they are in one of the offices. Additionally, (**2nd question**)how they can log on to the domain server when they are on the road like in a starbuck, what do they have to do to connect to domain after VPN connection are successful.

also it’s my understanding that, we can’t share resource from computers on different network segments, (**3rd question**)what is the best solution to bridge/combine two network segments(two office in different locations) so computers of different location can see each other.

Thank you in advance for any response.