Hi
I am 22yrs old and I'm 80Kg, I need to come to 60Kg according to my BMI.
I have only 3 months to reduce.
Please suggest me the necessary diet and excersise to be done.
I need to reduce 7Kg a months.
Please help!

DO you plan on living much past 3 months? And maintaining any of your health? That is actually way more than would be considered safe.. and enough to put your metabolism into low gear making a weight rebound immediately afterwards very likely.

A KG is 2.2 lbs in the US. So 80 kg is about 176 lbs

And to lose 20 kg is about 44 lbs. Sorry you will not and should not lose that much weight in 3 months, you may lose about 1/2 of it, but what is the issue, take time and lose it correctly.

Also how tall are you, since proper weight has to do with height also.