Is it true that alot of actresses don't know how to use a gun in reality?

Who would care, unless you are a stalker or a rapist?!

Of course. Most people aren't very knowledgeable about using firearms in general 

Most human beings in general don't know how to use a gun in reality.  There are a small number of gun nuts in the US, but they're not typical.  The average American has never even seen a gun in real life.

Unless a they're American or in the military/police or a hunter, why would they?

A lot of actresses don't even know how to spell gun.  We are not talking mentally elite here. 

Some actors or actresses probably practice and shoot weapons as a hobby, but I wouldn't say many. If the role requires holding a gun a lot, there might be an expert on set to go over basics so they hold it correctly etc. 

Very few British actors and actresses know how to use a gun. That's  because we don't obsess over guns like you Americans do. As a result there are very few gun crimes in the UK.

It's true a lot of people don't know how to use a gun in reality. It's also true that most actors and actresses aren't ever called upon to even pretend to use a gun, so that being the case and it being the case that a lot of people don't know how to use a gun in reality, it stands to reason a lot of actors and actresses don't know how to use a gun in reality.

That's why they call it "acting"...and they take shoot after shoot until the director thinks they got it right.