Here's a rough diagram of the apartment:
There's absolutely no air flow in the apartment, probably because of the directions (up = south)
The worst area of the apartment is the left section, as it contains heat-generating appliances (refrigerator, cold water bar, etc)
What would be the best way to ventilate the apartment? Will putting a fan on the window do the trick? What should be the direction of the fan - to insert fresh air from outside, or to exhaust hot air from the inside?
Usually all doors and windows are open except for the small window on the bottom-right side of the diagram.
Fans move air. If you need to move air in this apartment then fans will be your friend. Putting fans in windows will be the most sure way to get air to flow in or out without it just circulating around inside.
There are downsides of using portable fans: