7 kg is too much to lose in one month... the most you should plan to lose safely is 2.7-3.6 kg in one month.
Your ideal weight depends on your age and frame size.
In order to lose weight, eliminate sodas and other sugary drinks, along with chips and other snack foods from your diet. Concentrate on veggies, fruits, lean protein, whole grains, nuts, seeds and healthy fats. Make sure you keep portion sizes in check.
Be sure to get some exercise every day, even if just for a few minutes.