would think that they all were natural righties and then they learned to bat lefty at a young age, still that is very impressive.Is not it extremely hard to learn to hit from both sides?

Both.

Mantle and Jones are natural righties, meaning they throw with their right hand. Berkman, though, is a natural lefty.

It is interesting - most switch hitters actually r natural lefty batters, but righty throwers. Usually, though, u can tell what side of the plate a switch hitter is naturally better on by looking at their stats - switch hitters r usually better from one side of the plate than the other. There r a few bizarre hitters, though (Mickey Mantle is an example) who generally hit better from one side of the plate, & yet consider themselves better from the other side of the plate.

And yes, learning to switch hit is insanely difficult, & usually starts at a very young age, because it is even more difficult to do after years of baseball experience hitting exclusively from one side.

l know berkman is a natural lefty..

Mantle and Jones are natural right handed. Berkman is a natural lefty. You can tell pretty much by which hand they throw with. It is not 100% true all of the time but it is a pretty good indicator.

l know The Mick was a natural right hander.