[Q] Stuck in bootloop, recover files topic

Hello.

Today my oneplus one was suddenly stuck in bootloop. This happened in the middle of the day when I rebooted my phone. My phone was running the latest update that came OTA (stock lollipop). Whenever I boot my phone it starts loading and suddenly a Chrome (browser) window appears for 1 second and tries to load a website. Afterwards my lock screen pop ups for 1 seconds and it starts to reboot. During the lockscreen I tried to unlock my phone as soon as possible, but it just reboots. (Any ideas about this weird problem?)

I CAN boot it in recovery mode by holding volume-down button and power button.
I CAN boot it in fastboot mode by holding volume-up button and power button.

Perhaps a factory reset will do the trick, but I don't have a backup of my files (because this happened so suddenly without me trying to flash/customize my phone). My first priority is recovering my files, because most solutions will end up in me losing every file. Unfortunately I've found little possibility to do this during the bootloop problem. I've tried to flash TWRP because it could make backups of my phone. I tried it through ADB/Fastboot, but it failed because my device is not unlocked (I can't go to settings and put my phone in developer mode and debugging mode). So I've read somewhere that unlocking my phone (bootloader?) through ADB will wipe my phone, which is exactly what I don't want.

Also I've tried this: http://forum.xda-developers.com/onep...rrupt-t2879061
But It also failed because my device was not unlocked.

Did I miss some steps somewhere or did I read something wrong?
Hopefully anybody has an idea to either fix the bootloop without losing my data, or finding a way to recover my files before wiping the phone.

Thank you.