So What Is The Exact Number Of Sets I Should Do?

There is no set formula for any one person. What works for you might not work for me. What works for an 18 year old will almost certainly not work for a 50 year old! The truth is that it is trial and error. You will have to find the "sweet spot" in your training that allows you to stress your muscle fibers but also allows you to come back on your next session and blast them again. As a very general rule and depending on age and experience, hitting each muscle group twice a week should be something to shoot for. But if you are not making gains, take a look at both the number of sets you're doing and the frequency that you're working a group. Remember, sometimes less is more!