Another point for Stefen -- why do you want your weight to be 60 kg? That is pretty light, unless, of course, you're not grown yet. What is your age and height?
Stefen, if you have not already done so, speak with your doctor to be sure there is nothing triggering the weight gain (such as a thyroid issue) and then talk to the doctor about exercise and about what you eat. But do get a complete check-up too, you don't want to miss something that has a medical answer. It is never a bad idea to run your diet and exercise plan by a doctor, either, even if you do not have any medical conditions that contribute to weight gain -- the doctor is interested in all aspects of your health including staying at a healthy weight.
If you give more detail on what your diet is like and what your exercise level is and how old you are and whether you made some changes to your life that led to the weight gain you can get more help with this. But basically, every weight problem has the same answer -- eat better, exercise more.