You must read on flashing guides and be 100% sure you have read and learnt everything.
I could post a How To here, but if you got stuck or made a mistake you'd have to ask here again and maybe no one would respond for a while and you would be stuck. So it's a lot easier if you try to find for yourself so you can learn it, and maybe one day teach someone else how to fix
EDIT: I am not being rude by not helping, just I am trying to fix my device also after Hard brick
// LG G3 (D855) // Stock // Stock //
S3(White) > M7(Red) > Note 3(Black) > Nexus 5(Black) > M8(Gunmetal) > LG G3 (Titan Grey)