Singular or plurial after their???

Hello,

I hate to use "their" even in my mothertongue French as I never know if I have to use a plurial or a singular after it...

Here is my sentence:
You obtain detailed data about your visitors regarding their nationality, their language and regarding technical information, such as their operating system or their browser.

Sould nationality, language, operating system and browser be in their plural form or not??
Could you explain me when to put a "s" or not when using "their" in English??

thxs in advance
Ludo