am i using the alt mode if i see the live histogram?
No. But it does tell you that you have CHDK loaded correctly.
According to the CHDK manual i should see an <alt> icon (When you enter <ALT> mode, the indicator --ALT-- will appear at the bottom middle of the OSD). I do not see that...however i see the CHDK Icon.
When do you see the CHDK icon? All the time or just when you start the camera?
If i select a script (intervall.lua) from the intervall script menu and hit the shutter button the camera just takes one picture...I don't see any menu item that starts the script...
If you can see and navigate the CHDK menus then you are in <ALT> mode. Sounds like that is the case if you can go to the script select menu and pick a script. If you press the Menu button after that, you should see the name of the script on the lower left hand edge of the screen. And if you press the shutter button at that point, the script should run.
Update : the ELPH320 is a very new port and a touchscreen too. I guess its possible the LCD dimensions are wrong in the CHDK code such that the bottom of the CHDK display area is off screen?