Do pumps actually work ?

No, it very likely will not work. And the reason is because there's a very good chance that you will injure yourself, become discouraged, and give up.

I found that pump on Amazon and checked out its specs. The lowest level on that pump tops out at -35 kPa, which is equivalent to around -10.3 in Hg. That is an unnecessarily strong level of vacuum and really isn't safe to be using on a continuous basis. Personally, I would never use that strong of a vacuum when pumping. At -10 in Hg, you're way beyond the level of vacuum needed for permanent enlargement, so at that level of vacuum it's all risk (of injury) and no benefit.