Can I lose 20 lbs in 2 weeks?

No, losing 20 pounds in 2 weeks is not safe or realistic. This would require an extreme and dangerous calorie deficit. Healthy weight loss is 1-2 pounds per week, meaning 20 pounds should take 10-20 weeks. Any rapid weight loss that extreme would be mostly water and muscle, not fat, and could cause serious health problems including nutritional deficiencies, gallstones, and metabolic damage.