Begginer of airgun at Auckland

thank you mate.

Heard that someone just lost three fingers playing with PCP because of the failure of container.

Higher the altitude the thinner the air is, the thinner the air the less that will go into cylinder. So yes less power higher up.
You can buy CO2 guns, they are differnt from pcp and you don't need a licence to use them.
But they all have limitations.
Look up on the Web, what are the three main types of air rifle.
Then look up fps and fpe.
I can send you to a site that has a lot of info on stuff but you will need a basic understanding of air rifles, pellet speed and pellet energy (fps, fpe or what ever the metric units are.)
Probly pay to look up pellet types and weight as well as shape.
Then look up the difference between a target shooting set up and hunting rifle set up.
But mostly for now just enjoy shooting with your air rifle, have fun and as time goes by if you want to upgrade you'll have had plenty of time to learn what's out there but more importantly you'll have a better idea of what sort of air rifle will suit you better.
Oh look up triggers for air rifles too. They can make a huge difference to accuracy.
Have a read through the sig asp20 thread on this site. There's a whole heap about differnt pellets we have been using in them. It will give you an idea about how pellets affect accuracy.

Wow，thanks. but there are lots of panic buying when the covid-lock down is coming. what I mean is that if she really concern about self-defense and she won't win in a fist or blade battle against gangsters, should she directly get FAL and buy some semi-auto wapon like AK47 rather than low power airgun?