Share your experience!
I unlocked my bootloader and install Cyanogenmod. I realized that i wanted to go back to the normal xperia experience. When i wanted to delete cyanogenmod and install the original software but i deleted some wrong files and now my phone is dead. I cant turn it on the screen stays black but my led at the top still light when i but in the charger.
- Frederik
Xperia Z1
You could use EMMA to flash official ftf:
http://developer.sonymobile.com/services/flash-tool/how-to-download-and-install-the-flash-tool/
Thanks for quick response. I will try that! 
Keep us updated.
I installed Emma and now i need a login. I inserted my cridentials and now i wait for approval. How long is this going to take?
Just follow all the steps given in the link:
Copy the Customization.ini file. You find it in the Flash_tool_for_Xperia_X.zip.
Paste the Customization.ini file into the installation folder. The installation folder is the folder named Emma in the installation path examples on point 3.1 and 3.2 above
Ok now im in the program but my device isnt detected.
The led is "red". And when i try to hold down the volume down bottom and connecting the usb cable nothing happends.
Make sure your device is completely turned off by pressing power button+volume up at the same time until it vibrates 3 times.
I got my device listed on Emma and installed the (Service) Kit Kat 4.4 but my device still wont turn on. What do i do?
After charging for a nigh my device turned on and was fresh like out of the box. Thanks!