How to install a new Language?

COuld try changing the product code and then update your phone again, don't know if changing the product code to a german code requires update though, but use the search option to find out how.

I couldn't find something, using the Search in this Forum...

But, what happens with the Keyboard setting?? He has an "AZERTY" Keyboard, and if I change the Productcode of the N97, is this Keyboard supported or not?

1. Install Phoenix, and while the installation is running, load up Navifirm, in the left hand column. It takes a while to load the columns on the right, so be patient. Then click 11.12, then find the firmware variant you're looking for. For me, this was Taiwan Dark Grey it shouldn't matter which color you use, but pick your own color just to be safe, I think it just changes the starting theme. Then click "all" and then click "download from FiRe". Put the files in any folder for now, we'll move them later.
2. After you install Phoenix, navigate to "Phoenix\Products\". Then make a folder called "RM-596". Move the firmware files into this folder.
3. Launch Phoenix. Click File -> Scan Product. You should see the red light in the bottom right corner blinking. After it's finished, the firmware version should show up on the bottom bar, it should say RM-596. Then click Flashing -> Firmware Update. In the "Product Code" line, click the "..." button, a new dialog box should pop up and you should see the firmware that you just downloaded. Select it, then click okay.
4. Now, click "Refurbish" towards the bottom. Phoenix should start flashing the firmware onto your phone.
5. Once it's finished, let the phone load. Once your computer detects it again, It should be safe to unplug.
6. First thing to do is to SET THE DEFAULT LANGUAGE TO ENGLISH. You can do this in Settings -> Phone -> Language. We must do this BEFORE you download the OVI Store App, otherwise you will get jumbled characters in OVI Store! After you download the OVI Store with the default language as English, you can change the phone back to the language you want to operate in.
7. After everything is done, you should be good to go.
All The Best