Default Help Needed - brick

Hi. I was trying to restore my D802 with LG flashtool but it failes at 49% every time and gives me this:
02:26:57 : wParam : 13, lParam = 47
02:27:19 : wParam : 100, lParam = 3146241
02:27:19 : MODEL DLL Event : (100, 3146241)
02:27:19 : Step : TYPE_WPARAM_UPGRADE_ERROR
02:27:19 : CleanModelDll() : Free Model.dll
02:27:19 : _DetachDLL Call
02:27:24 : _DetachDLL Call End
02:27:24 : Page_Error 부분입니다
02:27:24 : 여기는 Retry 부분입니다

I flashed a wrong kernel version in twrp and ended up stuck in fastboot. Then I flashed the "right" boot.img via fastboot(very stupid) and now my phone wont boot at all.

It wont even boot into fastboot anymore. It just gives me the LG boot screen with "secure booting error" and "Cause: boot sertification verify". Seems like there isnt any boot.img at all. I can only boot into download mode.

Any help would be very appreciated. But I guees im out of luck this time.
HTC One (M8)