hi,
thanks a lot. I've done it, like written at
http://iphone.fiveforty.net/wiki/ind...1.1.1_to_1.0.2
Pharagr. B for "downgrading" to 1.0.2. ... after "jailbroken" I followed the "manual" of macwelt.de ... install SSH ... take a turbo SIM ... execute some commands ...
Now... 120 Minutes later my Iphone works

I havent tested thinks like EDGE but I can do normal phone calls ... use the internet with wlan and so on... the iPhone works now together with O2-Germany. I have looked up the "Modem Firmware" it is 04.01.13_G its the current firmware from 1.1.1 phones isnt it ?
greentings and thanks
Jörn