Can i tell me how i can lose 20kg in 3-4 months?

That's equivalent: To 44 pounds. The rate of loss you are suggesting in on the high side. You might consider losing this over 5 months or more. Eat healthfully ; be physically active. Aim for 7.5 to 8 hrs of sleep / night. Hydrate w at least 64 oz of water / day. Calories burned must > calories consumed. Do both cardio ; weight training. You can mix ; match different kinds of physical exercise.