The number of approaches for each muscle group depends on your ability to cope with the training load, life circumstances, nutrition and other factors. I recommend doing from 6 to 16 working sets, most people progress well on 9-12 approaches. If you do so many sets, and the muscles do not receive the necessary stimulus, then you need to stop relaxing in the gym and start working.
Don’t you think so? You want to say that you can do more than 12 sets, giving all your best, and recover well after that? Well, it happens. Some are really capable of this, but they are rare exceptions, and you better start by assuming that you are not one of them. I understand that this somewhat lowers self-esteem, since everyone considers himself special and very cool, but I want you to understand too: surviving a tough workout is one thing, and recovering and growing after it is completely different.
Start with 9-12 approaches and practice like this for a while, doing your best in each set. See how your body responds to such a volume. If you are absolutely sure that you are doing it and you need extra workload, then I allow you to add more approaches.
Remember also that 9-12 approaches for each muscle group is still a general recommendation. If you have low recovery abilities or you are very busy at work, the range of 6-9 approaches is more suitable for you. In training for the whole body, the number of approaches to individual muscle groups should be even less (4-6), since the total training load will be quite large.
Test to determine the maximum number of approaches for each muscle group.
There is a simple test to determine the maximum allowable number of approaches performed for a particular muscle group. To do this, you need to take the weight that you can lift to the biceps without cheating 10 times (but not more). Then you need to measure the girth of one of the biceps in a stressed state, and begin to lift the biceps by approaches 10 times, after each set again measuring the circumference of the biceps on the same arm (naturally, in a stressed state). After each set, give yourself such an amount of rest that will allow you to once again lift the same weight 10 times (but not too long). From approach to approach, the circle will increase, until after the one it stops at what has been achieved or loses in size.
This number is the parameter that interests us. The number shows the maximum allowable number of approaches to biceps. Suppose your bicep circumference has stopped increasing after the fifth approach, which means that the maximum number of sets for your biceps is 5.
For the remaining muscles, use the following ratio:
Broad back muscles, quadriceps, large chest muscles = N + 4;
Triceps, hip biceps, glutes = N + 2;
Press, long back muscles, lower leg = N;
Deltoids, forearm, trapezoid = N-1.