No ROM (OS) no recovery mode. Only download mode works

Hi @ all.

At first sorry for my bad english. :(
I am having a LG G2 D802 International.
I rooted my device and installed CWM. I started CWM via the APP "ROM Manager". I download the CM for the device and tried to install it.
I wiped the data and the dalvik Cache into the recovery mode. Then i tried to install the CM via an adb command. But it did not work very well. So i thought "Turn the phone off and on again" and now the issue appears. If i try to get into the Recovery Mode it does not work. It does not boot because there is no ROM on the device anymore. Only the message "Security error" appears. I only can get into the Download Mode and into the Settings for the Hardware keys.

I tried it with following Hardware key combinations:

Download Mode: Volume UP + Power Button (WORKS)
Recovery Mode: Volume DOWN + Power Button (DOES NOT WORK)
Hardware Key Settings: Volume UP + Volume DOWN + Power Button (WORKS)

Does anyone know what i can do? Anything so i can get a ROM on the device?
Sorry for this lame post.... :crying:

Thanks in advance!

BR,
Highdox