[G3 Q&A, Help & Troubleshooting] onskulis:
Hello. Im sure there is plenty of such topics in the forum, but I believe, that my case is specific and I hope we could resurrect my phone somehow together.

So last night I just send a WhatsApp VoiceMessage to my friend as suddenly my phone started shutting down, just like if it had 0-2% battery power... But it actually had over 40% battery life... I thought ok, yeah, might be battery, so I plugged in the original charger and the phone didn't show any signs of being alive. Then I've unplugged charger, toke battery out, plugged charger back in and I saw that its still alive, telling me "please put the battery in, there is nothing inside me to be charged". So I placed battery back to the phone and guess what.... It shows no signs of being alive again, the battery wouldnt charge... Then out of panic I started to do random stuff like holding power button for 10secs for soft restart, holding power button and volume down button for what ever that was... Plugging charger in and out like crazy... The phone was just dead! So I had to give up... I toke the battery out and let the phone lay for like I dont know 2-3 hours. Later on, I came back, put battery inside and tried power button + volume down again.... woohoo!! , it worked, my phone started to boot! I thought this is it! Hes alive again, but ahahaha.... 6-7 secons during the boot, it just turned off immediatly. I thought yeah, must be battery, so I order new, original LG G3 battery... And while the order was on his way to me, I managed to charge the old battery after letting the phone lay for 2-3 hours and then plugging charger in again. It started to charge... I let it go up to 66% I believe and tried to turn on the phone again.... Guess now what? LG intro screen poped-up and the in left corner I just saw something with "boot error blah blah geeky stuff" and suddenly red and blue LED started to blink, red/blue/red/blue/etc... and the screen just turned off.... I couldnt do anything.... So I removed battery again and waited for my order... Next day I got no success turning my phone on with new battery.... I was playing around with different button combinations and remove/put battery and conclusion is.... The phone is dead except if you let lay without battery for few minutes... Then you can start charging battery for example... After that you can try to boot it, but it will just shut down immediatly after few seconds. Or you can try to boot it, but again, it will shut down immediatly and then you cant do anything until you let it lay without battery. I also managed to access recovery mode but I didnt start it, because I would like to get at least my data back somehow.... The phone is not that important as the data on it. I also tried to access download mode, for recovering my data, but without success....

LG G3 D855 Europe version

Lollipop 5.0 OTA version

Not rooted, Not modified

Any help would be really appreciated. If its impossible to resurrect the phone, can I save at least my data somehow? What would I try, please?

[Edit]

I just tried to start factory reset for sake of god.... Found some data recovery software on the internet, that might help after factory reset, but phone just shut down immediatly after I confirmed that I want to reset and nooow.... I see the LG logo like it would try to boot for already 20minutes and nothing happens