I calculated in [here][1] as it says 65kg male 175cm 29 yo, needs 3000 calories a day with following Activities every day. and I eat 500-1000 Calories everyday It means I lose 2000 Calories every day. 1 kg mean 7700 Calories(theoretically) so I need to lose 1kg every 4 days? Is that right?
1 Walking >> 5.5 km/hour 336 Calories Burnt
2 Sitting >> 720 minutes (12 hours) 1080 Calories Burnt
This kind of extreme weight loss program, as Larissa mentions, will have a negative impact on your body, and additionally will not be very sustainable. Based on your weight, and your description of your body, a far better path to achieve your goals will be starting a weightlifting program with a controlled diet.
While your main goal may be a flat stomach, you'll find that you see the greatest improvements with lifts that incorporate many muscles, such as deadlifts, squats, or bench press. I won't outline a weightlifting plan here since you didn't ask for one, but know that these sorts of exercises will lead you to the results you seek. If you definitely need to lose weight, then keep your diet at a normal level as you begin to exercise; the deficit created by working out will lead to lost weight. I'd recommend, however, with your weight, that the best strategy would be to eat a little bit more, add some protein to your diet, and focus on muscle gains, as these will bring you closer to the body I think you're looking for than pure weight loss will.
As a side note, you may have a normal amount of fat on your but just lack muscle underneath. Web MD offers a good summary of the role of stomach fat and explains how everyone has fat there to some degree. If you're in this situation, weightlifting is definitely the strategy to follow :)
