Okay, for muscle mass in the biceps, I do dumbbell curls. At the moment I am doing dumbbell curls with a 28 lbs dumbbell till failure (usually 6-8 reps)
How many sets should I do?? How much rest in between each set also?
Thank you.

I want to grow up bigger bicep.I have two 20 pounds of dumbbell and I do 20 reps of 8 sets of dumbbell curls three days a week,am I over training please suggest me.