I can understand as I also faced same problem and felt very helpless because it is not cheap phone.
Also downloading these huge fw files consumes lots of data.

But Can you try to download UAE fw and check? It have higher version number than german. I am suggesting this because you can at least try to get phone working in such condition that you can see wlan and bluetooth id and no longer sim error while startup.
This will allow you to use it for all functions except telephony.