How many piercing is it possible to have?

Yep. 3 is a good limit. And you want to wait about 2-3 months(at the least) in between piercings that you get at different times. If you get a bunch of piercings at once, your body has a harder time healing all of them so they stay angry longer and your immune system is spread thin so you have a greater risk of infection. You should be fine with 3 though.