Cyanogenmod won't start/ pink screen on boot

Hello everyone,

I've got a big problem flashing Cyanogenmod on my Samsung Galaxy S4 (I9505/ jfltexx).

When I first flashed the phone, everything was fine. Then I rebooted the phone, but before I entered the pin of my Sim-Card I shut it down. When I tried to boot it again, later that day, I just booted into a pink or magenta screen. Since then I was not able to flash anything to my phone - due to that screen.

I read, that it might help to reflash the stock firmware, so I tried it. But I was not able to flash that because in the middle of the flashing process the phone always crashed. Sometimes I am able to flash Cyanogenmod onto the phone, but the boot process of Cyanogenmod will be interupted from that magenta screen every time.

Today I wanted to try it again, downloaded the latest Cyanogenmod 12.1 nightly, the nightly of Cyanogens recovery, flashed that and then tried to flash Cyanogenmod via this one. In the past, I always used clockworkmod recovery.

But this Time the flashprocess got interupted at 47% - of course the pink screen wouldn't let go. :(
Terminal output (nothing really interesting, but maybe someone can see something special...):

Code:

---

$ sudo adb sideload cm-12.1-20150922-NIGHTLY-jfltexx.zip
loading: 'cm-12.1-20150922-NIGHTLY-jfltexx.zip'* daemon not running. starting it now on port 5037 *
* daemon started successfully *
serving: 'cm-12.1-20150922-NIGHTLY-jfltexx.zip'  (~47%)    * failed to read command: cannot connect to daemon

---

After that last try the phone seems dead (or bricked) - it won't boot. First it didn't boot into Download-Mode, but now it does not seem to do anything.
// edit: I'm able to enter the download mode again. Taking out the battery for a few minutes seemed to help.

All in all I'm trying around for nearly three month. Thank you very much in advance for any idea given.

Regards,
baronBale