I think, a category per language would make the forum confusing for most users because they won’t know where to post.
E.g. I am from Austria and speak English:
- Should I post in the German category or in the “Fairphone Help” category?
- What if I want to talk about “Software and Apps”, but in my native language? There would be only one German category, not divided by the topic type. It would be a mess.
To argue further against the necessity of a category per language, I did a little research:
At first, please, have a look at the Fairphone User Profile Infographic (PDF). You will see that 84.3% of Fairphone users come from one of these countries:
- Germany
- The Netherlands
- Switzerland
- UK
- Austria
- Belgium
The EF English Proficiency Index (using test data from EF) says that adults from these countries in average either have 
Very Good Knowledge or 
Good Knowledge of the English language.
Thus I think it can be expected that over 84% of the Fairphone community are able to follow the discussions here on the forum and contribute their own comments.
As for the other 15.7% of Fairphone users, many of them are from Scandinavia and are also expected to have Very Good Knowledge of the English language. The very active communities in Spain and France (adults there in average have Intermediate Knowledge of the English language), have their own topics and the current modus operandi is accepted by the communities in these countries and does not need to be altered.
Bottom line: Why make it harder for everyone to follow solutions and discussions on the forum, if only a small minority is not comfortable with the English language?