In the manual it says to select a program and to modify it to the individual requirements. Do I have to save them always in the different voice banks or can I create a new folder with all my individual programs ? How to avoid overwriting existing programs (happened when I modified existing ones even when I saved them under a different name).

The PROGRAM LOCATIONS unfotunately are fixed and so you simply over-write the factory ones. To store the factory files so that you can always revert to them when needed, make a back up of the following file in your AUDYA's HD (which is where the programs get stored) ...

C:/SYSTEM/INIT/PRESETS.PRG (make a copy of this in another folder (e.g C:/WAVE/DEFAULT). This way you can change your programs as you see fit, but when you want to get back to the factory, simply copy this file back into the location above.

...When you press SAVE - you're saving the currently selected PROGRAM into memory (on the panel), i.e simply overwritting the current PROGRAM in memory with your new one. When you press SAVE DISK, ALL Programs are saved as 1 file to the Hard Drive - PRESETS.PRG