Is there anybody who can help me with config the left cargo door of the PMDG777F?
You don't need any configuration, because the airplane is already configured in GSX internally so, unless you do *not* want to use the left cargo door, there's no need to edit the airplane.
To Undo all your changes, and revert the airplane to the configuration that comes with GSX, select the "Reset" option in the airplane configuration editor.
If you downloaded a configuration file, maybe made by some user before the airplane was internally supported by GSX, and you placed it into the main FSX folder (instead under %APPDATA%\Virtuali ), resetting the default configuration with the "Reset" button it's not enough, and you'll also to remove any GSX.CFG file you placed in the main airplane folder.
This will ensure you are using the default GSX configuration for the 777F, that already supports cargo on the left door.
In the aircraft settings there are only passengers door visible on the left side and no cargo door
as you may see in the screenshot..
Those labels are not supposed to "move" in that diagram, which is just an example. What counts are the coordinates, that are indicated in the sim by the pointing arrows with the name of the door, and the type of the door controls which service will get there.
So, if the airplane wasn't supported by GSX and you had to create a new configuration for it, to move a cargo door on the left side, you simply select one of the two cargo doors, and MOVE IT to the left side of the airplane, in the 3d editor, and ROTATE the green arrow by 180 degrees, so that it will point towards the OUTSIDE.
But you don't have to do this at all, with the PMDG 777F, because it's already 100% supported, with no intervention required.