Is it right to lose 5-6 kg in a month?

This totally depends on where the person is starting from. The recommended average rate of fat loss is 1lb./week. A more specific guideline would be 1-1.5% of bodyweight per week. So if you are 105 kilos, 1% would be 1.1 kgs per week or 4.5 kgs per month. This is only if you want to lose fat while preserving your lean body mass. If you try to lose any faster, there is a chance you will lose some lean tissue and have some deficiencies in the long run.