do i only do 2 sets for a full body workout ?! or i can do more ?!! what about the reps 8-12 which is the best to do 10 ?!!
You can do as many sets as you want. A good rule of thumb is to lmit your total sets to between 20-25. If you want to do 10 exercises you can fit in 2 sets of each, 4 exercises you can do 6 of each.
is it ok to decrease the weight i use to carry ?!
I'm not sure I understand the question but if you are asking if it's OK to use a lower weight, yes. In fact you should at times. if you are working on technique or cycling rep ranges or doing active recovery you need to.
i'm doing 3X5 now and i carry heavy weights, but i'm sure that i can't do 8-12 with the same weight coz it's heavy. i'm i not benefiting when i decrease the weight ?!! coz i use to carry heavy weights and then lighter ?!!
8-12 will be harder than 5 reps because its more reps. That's normal. There should be a rep range calculator on this site but I can't find it. I know 5 reps = 87% of 1RM but 10 reps = 75% 1RM.
i'm not into bodybuilding as i said before, don't want to bulk up just maintain as i'm know.
Many of us are in this position. As you get older it becomes increasing hard to hold onto your strength and power. Size becomes less important. At my age, no one cares how big you look. People are most impressed by a lack of a beer belly.