Make sure, you are using correct Sample Rate - the same in the project, the same on your audio interface, and the same during export.
No, we can’t.
You need a audio interface with these Inputs. If you already have, set this device in Devices > Device Setup > VST Audio System. In VST Comnections > Inputs, add a relevant busses.
I would recommend you to watch Cubase QuickStart Tutorials from Steinberg official YouTube Channel.
Also check to make sure the right and left locators are set to include the entire track. I’ve made the mistake in the past by not setting the right locator to the end of the song…might be it