I can also only advice to use paypal. I am german as well and paypal is free, the payment with it on ebay and other online shops is very uncomplicated. Actually once you successfully registered it is only a matter of clicks and it translates currencies immediately, so it is really good for anthing concerning international payments. Just check paypal.com and see how it works.

Ok, thanks for all your replies. I will have a deeper look at paypal to see if it works with only a cheque account.

Thanks for the links and the advice.

Yes, I prefer to play in french, so this can be useful.   

My DL version is v1.4x, (box version updated with galactic_civilizations_ii_dread_lords_patch_v1.40x_multi-langues_26993.exe).

I will try to download the english version with SDC (or may be Impulse) to check my serial id, and if it works, I will go certainly for this pack:
Galactic Civilizations II - Expansion Bundle $44.95 [Digital Download Only] WWW Link
It doesn't seem available via TGN with Tokens at this time.

I would try to install both versions at the same time (one in french and the other in english), but I don't know if it's possible.

The unofficial french translation seems to replace english files, what will happen when new patches are available and some files are replaced, there is certainly a need for a new install of the french translation (after a new translation).
Can this unofficial french translation be used as a Mod (start the game in english and select the Mod "french")?
Maybe a solution to be considered to address the problems posed by the English version patches, and so, always have an english version to date and "clean", then replace the Mod "french" when available.