I'm sorry there went something wrong in my last answer. I wanted to send the following text:

Ok I have tried to use bcpvpd but it was not working because of an incorrect input file format.

So I have done the following steps now:

1. Extract the .wph file from Bios .exe file (result see my last answer)

2. Loading the .wph file into Phoenix WinPhlash v1.7.16.0 to get some more information about the Bios (see attached log file)

3. Decompressed the .wph file with PhoenixTool v2.11 into several single Bios module files.
I guess it is the same what bcpvpd would have done.
So it seems you are right that the Bios file is compressed because the folder of extracted wph has a size of 2.497 KB which nearly match the chip size. You can check the other 2 attached log files (one is the decompressing log and the other one the folder structure).

So at last I just need to know now how I can merge the needed decompressed files back into a flashable ROM file.

Can someone help me? I hope the log files give some more information.

Thanks and regards,
Daniel