Help Galaxy S2 stuck on Cyanogenmod screen - Help

[CY87]

Hi!
My phone (Samsung Galaxy S2) randomly got stuck so I took out the battery and turn it on again, but now it is stuck on the Cyanogenmod screen (with the turning blue wheel).

Unfortunately I don't understand much about this or how to fix it since my ex installed the Cyanogenmod on it about a year ago.
I've tried to look for answers in forums but all I saw was people having the same problem after flashing or installing or updating their Cyanogenmod. To me it happened without trying to do anything special to the phone, and only after the phone got stuck on a random app. (It happens a lot and I usually take out the battery and it comes up fine afterwards).

I would really appreciate any help!
I want to fix it but most importantly I would love to copy all my files (pictures and contacts) to a backup drive if fixing it is impossible.

P.S. because I really don't understand much, please explain the steps I'll have to do in the most detailed way...

Thank you!

 

[SavageRobot]

Hello,
First off I suggest you should probably post your problem here unless a mod can move it in the meantime or search those forums
Galaxy S2 (International) - All Things Root
Do you know how to boot into recovery? I THINK you keep hold of power, volume up & home buttons when the phone boots up, but I haven't had an S2 for ages so can't really remember.
Then I would suggest you navigate to wipe cache and dalvik cache. Reboot and see if that works before trying anything else.