some problems with my i9305 after installing CM12.1 -> I hope you can help

Hi there,

my plan was to install CM 12.1 with the help of this site:
http://forum.xda-developers.com/gala...5/rom-t3066156

At first, I used Odin to get TWRP on my phone. With TWRP I did a complete backup (EFS, Boot, Cach, System, Data).

Actually, I thought I have done everything like it is instructed on this page.

->
"First time installing CyanogenMod 12.1 to your Galaxy S3 I9305, or coming from another ROM:
- Read known issues ans FAQs
- Flash one of the recovery images (CWM or TWRP)
- Copy GApps and CM12.1 ZIPs to your SDCard
- Boot into Recovery
- Flash CM12.1 zip from SDCard
- Flash GApps zip from SDCard
- DO A DATA WIPE / FACTORY RESET (otherwise your device will be stuck at boot)
- Reboot
- Don't restore system data using Titanium Backup!
- Restoring Apps + Data might cause problems and is not recommended, avoid it if possible!"
<-

After installing GApps, I wiped all data on the internal storage, did a factory reset and rebooted.
Unfortunately, I have been stucking at boot. There has been only the CM symbol on the display.

With TWRP I restored my backup. After that, my phone has been booting normally, but it could not find any mobile service.
According to the settings, my phone didn't recognise my sim card anymore.
(After using Odin, I did a reboot and noticed already that my phone hasn't got any mobile service anymore. Can this be?)

Moreover, I discovered that I my phone has got difficulties to copy things from the computer to the SD-card or to the internal storage.
Even copying things from the SD-card to the internal storage, or the other way round, using a file manager app like "Astro" is not working.

I tried to do a factory reset, but then again, the phone stucks at boot. On the display just appears "SAMSUNG".


Can you guys please help me to get back to a working phone?


With best regards,
New.Android.User