How do i loose 20 pounds in 40 days?

That's too fast: It's possible to do, with help of a doctor to monitor for side effects, but losing a half-pound every day for 40 days is too much too fast. One likely will get sick, and the weight will likely come back after the 40 days. It's possible... but one would have to exercise all day, drink the proper zero-calorie drinks to stay hydrated, and eat small amounts of just the right foods to stay in balance.