I am using dumbbells three times in a week. I have 9kg and 11kg. I am doing two workouts and I count until 25. I am doing 2 sets on 9kg. After this, I immediately do 11kg for the same workouts until the number 15. I am doing two sets. Should I increase my sets or should I workout more often? I want to increase my muscle size on my biceps as fast as I can. I'd like my arms to improve in one month and for them to be more visible.
Just to be clear, bodybuilding is a sport of patience. You won't achieve your goals in 1, 2 or even 6 months.
That being said, if I'm reading your question correctly, you're already doing sets of 25. In this case, you're better off increasing the weight, rather than the amount of reps or sets.
If you can't increase weight for some reason, you can try different variations of bicep curls, as well as concentrating on the negative part of the movement. Try some sets going up in 1 second, and down in 3 or 4 seconds. You'll find out it will get increasingly harder to do.