That depends on if you mean by geography or culture. By geography, Norway is closest to Sweden, but culturally, Norway is probably closer to Denmark.
Oslo NorwayOslo is closer ...it's a bit over an hour closer than it is to Helsinki
Greenland is between North America and Europe, but closer to North America.
No! Finland is next to Sweden and Norway. The North Pole is at the top of the world!
All the locations you name are in the Northern Hemisphere -- closer to the North Pole than to the South Pole.
Greenland is geographically closer to Europe than Asia. It is situated in the North Atlantic Ocean to the northeast of North America and approximately halfway between Europe and North America.
Greendland
That depends on what you call 'close'. Greenland occupies the range of longitude between 12.14° and 73.02° west. So the only sure thing is that there are parts of Greenland that are 60 degrees closer to the Prime Meridian than other parts of it are.
Denmark
Because its closer to the equator.
Estonia is much closer to Sweden than Greece as it is just below Scandinavia, whilst Greece is in southeastern Europe.
They are both in Sweden. Gothenburg is a city, and Arlanda is the capital city's airport.