Can't run my device after bug/auto-restart. Need help with ADB / reset via PC

Hello. I probably corrupted some system files, because my device (lenovo P70) restarted automatically and now can't run. When I try to restart device it loads to pin-enter screen, then restarts in a minute or immediately, when I touch the screen. After this device loads bootloader - IMAGE: vgy.me/TJtRED.png - but I completely can't do anything with this screen, buttons doesn't work, and the arrow automatically jumps between options every 0,5s. If i unplug battery and restart - after 2/3 resets device turns back to this bootloader and nothing works.

I installed "Android Studio", Android SDK, I can run ADB, but my device can't be found via USB: IMAGE: vgy.me/IJqYrN.png

Also I downloaded USB driver (which should be installed, I used my device with USB before), but I don't know how/where can I install it: IMAGE: vgy.me/RCeZI8.png

So basically - I don't know how to reset my device, because it's suspended on bootloader.

I will be really thankful for any help. If I don't explained it enough, please tell me.

Recovery mode in inaccessible from my device. Neither button works, so I can't enter into recovery mode.
On this screen - vgy.me/TJtRED.png - I can't choose anything, because arrow automatically jumps between options every ~0,5s. The only way is to unplug battery, then after 2-3 restarts my device is back into this screen

— modified on Jan 12, 2018, 2:19:12 PM

PC can't see device plugged in via USB in any moment. I am using the same USB port and the same cable which I used to copy files between smartphone and PC.

Okay, it's at least strange. I put my smartphone into the... fridge (~2°C) for 2 hours, then it... started and worked for around 15 minutes. After this time in room temperature it restarted again and can't boot.