Yes this can be done. You could manually export the Google calendar and then import into the O365 calendar, or you could use a third-party tool such as BitTitan MigrationWiz to achieve this.
When I added an event on the Google Calendar, would it sync to the Office 365 group calendar? My whole team uses the Google Calendar, we just want to add it to Office for scheduling reasons.
Once you have synced your calendar to O365 using a 3rd party tool (or other method) you should stop using the Google calendar, as anything added to the Google calendar after the sync would not show in O365 unless you performed another sync.
