Mmm okay just askin cuz I was told to use powerbreathe that way I can stretch my lung and help to breath slower.
If you are a normal, healthy person, your lungs do not require any sort of stretching or training and doing so will not improve your diving. In fact, lungs are not balloons and were not designed to stretch.
You can't "breathe slower" simply by having "stronger lungs." Respiration is controlled by a number of factors including workload and anxiety and CO2 content. The way to use less air while SCUBA diving is to be a better diver. When you're relaxed and learn to maintain horizontal trim, learn how to weight yourself properly, learn how to kick efficiently, and a handful of other skills, you will then use less air.
An even bigger issue is that as a new diver you should be concerned with learning to dive better and
not be worrying about how much air you're using. Except for teenage girls and little kids, pretty much all new divers suck air like crazy. It's just part of the deal.
If your buddies are giving you a hard time because you're cutting their dive short you can either make arrangements for bigger tanks, or even better, find better buddies. Nearly all long-time divers get a huge thrill out of watching new divers see the underwater world for the first time and you should have no problem finding qualified buddies that don't care if your dive is 30 minutes.
Get certified (if you aren't already), go diving, and enjoy yourself. Efficiency will come later as you get better.
flots.