How much should i work out if i have to lose 2 kgs (4.4 pounds) per week?

You should get at least 60 minutes (1 hour) of exercise each day for the rest of your life basically! Your best bet for losing weight is to push yourself so that you get a good sweat. Walking is a good exercise to do each day for 30 minutes at a fast pace, like speed walking. Listening to fast music helps motivate you also, so try that. For 20 minutes every other day you should weight lift with two 4 pound weights. It will help build muscle and speed up your metabolism, and since you're a girl you won't get too built up and manly looking. And remember, the key to losing weight and being healthy is 50% exercise and 50% nutrition.