Intex Air Mattress

It has a one-way valve, I may be dumb, but then I remove the valve thing to do is let the air out there do not seem too easy and I do not want to tear my new air mattress .

It is supposed to be "not easy" to get out of the valve, otherwise it might accidentally press when you do want.
The best way to flatten an air mattress when you open the valve (if you can store or transport) is kneeling on the ground and start rolling to the opposite end of where the valve. As you flatten and roll, tuck the party rolled under your knees and press the air, keep rolling and tucking. When you have all supported and rolled tight, then close the valve so that air can not get it. If there is still a little awkward, you can pick through the valve to close.

I have a self-inflating air mattress for hiking, it is supposed to deflate over time, but you can simply suck the air, then seal the valve, or at least thats what I do with mine.