ok so heres the story i actidently erased my save file on ps2 so i had to do the game over again I am at Kasikstan and I fell off the ledge by the big gun thing and I cant get back up back up because the doors are stuck and I cant get through!

Where are you in Khazikstan exactly? At the beginning?

I know where you're at (at least I think I do), and it is a royal pain to get back up. There's a big machine-thing at one end (if you stand with the gun above and behind Lara, the machine-thing will be at the far left). Go to it. There are climbable poles, there, but you have to watch out for the electricity that crawls up the poles. Time it right and climb up. At the top, you'll be able to see the gun but you won't be able to get to it because the doors there are closed. Go through the other doors (follow the tracks in the floor) and navigate the myriad obstacles and you reach a large room.

Work your way around the room to the control booth up and at the far end of the room. Flip a switch, get back onto the floor, and use your grappling hook to get the cube-generator-thing along the tracks back into the hall with the obstacles. Timing things right, you can move the now-electrified poles and follow the cube-thing back to the other room. Open the door to the machine to let the cube-thing in and power the machine-thing. Make your way through the doors you couldn't enter before, look at the shield, and continue onward.

If any of that didn't make sense, read Stella's guide here and do a search (Ctrl-F in most browsers) and search for this term: "LARGE ROOM WITH TESLA GUN AND TOWER". Read from there.

Hope this helped.