I’d be certain it was the BIOS that needed changing before I got too carried away.
You need to check the Sony support site and find the BIOS update utility for your machine. You need to check the English site and locate the BIOS update utility for the English model.
Have some kind soul with an English machine download and run the program, terminating after the files are extracted and the bios update program offers a cancel option. Have them email you the bios data file.
Do the same on your machine, replacing the german bios data file with the english. Then run the update utility.
Gameson recently did this to upgrade a TR2 bios to TR3 and can provide more details.