If I may, what's your height.
Because your weight should be in accordance to your height.
Calculate your BMI and see if you are overweight, if your BMI falls in the range of 20-25, you are normal, if it's more than 25 only then you are overweight and only then you need to consider losing weight.
If you are having a BMI of above 25,
Here are a few tips to reduce weight.
1. Drink lots of water.
2. High protein, low carbohydrate diet must be followed.
3. Intake of calories should be less than the daily requirement, and you should get most of the calories from fruits and vegetables.
4. Avoid rice and rice products. Green tea twice a day.
5. Burn more calories than you have taken. Cardio workout must be followed. Any form of excercise which keeps your heart rate raised to a level of 140-150 burns fat effectively.
6. If you are very dedicated and follow all these sincerely you would be able to lose 15kgs in 4 months.
All the best.