@AdhamFH
Yes, your parameters for the function are not correct and you will get that error.
Please review the docs for the Get calendar view of events (V3) to understand what you are passing (and I'd advise using the V3 rather than V2 as it is deprecated). Most importantly, you need to pass the ID of the calendar that you want events for. Passing a name is not sufficient.
What I would suggest is to change your DropDown Items property to this:
Office365Outlook.CalendarGetTablesV2().value
And set the display field to name.
Then in your event gallery items, set to something like this:
Office365Outlook.GetEventsCalendarViewV3(Dropdown5.Selected.id, DateAdd(Now(), -10, Days), DateAdd(Now(), 10, Days)).value
Set your start and end dates in the accordingly - the example above will show 10 days prior to 10 days future.