How should I handle food that sticks in stainless steel pans or woks after cooking in sunflower oil?
To prevent sticking, your pan surface should be around 150 to 160°C. The farther away you move from that (higher or lower temperature), the more likely that your food will stick. So the temperature is very important, but without knowing how you are cooking, I can't tell you if you need more or less heat. 

If you have a layer of food which sticks, but hasn't burned, scratch it with a spatula and stir or turn. If it is burned, remove from the heat, scoop the food above the burned layer, and, if not yet ready, continue cooking in another pan. Be careful, because if you include flakes of burned food, your whole meal will taste burned.