Samsung Galaxy S2 GT-I9100 does not take on CM - E:signature verification failed topic

Dear all,

I got a Samsung Galaxy S2 GT-I9100 with a German Telecom Branding which I wanted to get rid of.

I chose Cyanogenmod and followed an online instruction to install it.

At first, everything seemed to work out fine, Cyanogenmod started, but then the keypad stopped working and I got this message that I cannot even recall (something like "..had to be closed down").

After reading some threads, I decided to do the whole process again, and (don´t ask me in detail what I did, but) now my notebook does not recognize my phone anymore and I cannot re-install Cyanogenmod.

I guess I will not be the first to ask this, but I could not find a thread that matched exactly my situation.
I am starting to get really exhausted.

Here is what information I can give - please forgive any ridiculous naming or expressions, I am not so familiar with this all:

I used CF-Root-SGS2_ZS_OZS_KG2-v4.1-CWM4.tar as a kernel.

I used Odin 3.07 for getting it onto my phone.

For Gapps I used gapps-jb-20130812-signed.zip and on ClockwordMod Recovery v4.0.0.2 this can be installed without a problem.

For Cyanogenmod I used cm-10.1.3-i9100.zip

As Cyanogenmod would not install, I tried to:
-wipe factory/data reset
-wipe cache partition
-wipe Dalvik Cache
-format system/data/cache (I guess I acidentally formatted the sd-card, as this, since, does not contain any data)
-toggle signature verification
-even tried toggle script asserts

I re-flashed the Kernel, and used an external SD-card to get Gapps and Cyanogenmod back into the phone.

I erased the necessary lines in the cm-zip to get over Status 7 which then had appeared.

But still the installation of Cyanogenmod does not work.

It now states:
E:signature verification failed
Installation aborted

and I cannot find any advise that I did not already try.

Can anyone help?

Greets and thanks!