I unfortunately bricked my phone. I started with downloading ODIN and CF-Root-SGS2_XW_CLK_KF3-v4.0-CWM4. I was able to get into the download mode and open the .tar. This was succesfull, I got to see my homescreen after the reboot. After that I made a backup using CWM.
And this is where I made the mistake. I opened CWM and opened cm_galaxys2_full-65 by using Flash an update. The device booted and started to install this and afterwards got stuck at the yellow warning sign!
I was hoping to fix this by going to the download mode and using ODIN again but this didn't help.
How can I fix this?