One thing that's very hard to translate comes from my native language - Slovenian. The grammatical number 2.

The same way most languages have singular and plural, Slovenian also has dual. It's much handier than always specifying "two somethings". Very few languages still have this feature. English for instance only has residual traces left.

https://en.m.wikipedia.org/wiki/Dual_(grammatical_number)

You can translate it, of course, but it's going to look and feel awkward.