Hi, thanks for quick reply.
I was watching YT on my phone and then fell asleep, so I suppose it just kept playing videos and that's why battery was at 0%. I plugged in my charger in the morning but instead of charging it started Firmware Update which was stuck at 0% for like an hour.
Anyways I manage to solve it. I held power button down and nothing. I held power button down and volume up as I read somewhere that it will hard reset the phone and nothing. Turns out on LG Q6 you need to hold power button and volume down for it to work. It restarted my phone that way and is now working properly again. Hope this helps someone.
Thanks anyway.