Ginong Pratidino Rosandaru
Ginong Pratidino Rosandaru answered question

20 kg for 1 months ?? That's to much bro... For healthy reason maximum weight to reduce is 2-3 kg per month. And also you didn't mention your age. If your age is under 17, it's very dangerous to reduce 20 kg for 1 months..

Just slow down and everything is gonna be okay....