Not a suggestion. If you wish to see a language available in a particular language you can always translate it yourself, provided you've completed the kata - after that you should be able to see an Add New button at the bottom of the language dropdown list.

At which level I'm allowed to translate?

Any. If you want Rust for this Kata, then you can translate it whether you're 8kyu with 2 honor or 1kyu with 9000 honor. It doesn't matter at all.
Here are some articles on translations:
https://github.com/Codewars/codewars.com/wiki/Kata-Translations
https://github.com/Codewars/codewars.com/wiki/Tutorial:-How-to-translate-a-kata

I'll mark this as resolved, but please do ask if you have any further questions.

For this kata the real numbers in use are whole numbers (4, 8, etc) and rational numbers (15.16, 23.42, etc). It does not include irrational numbers (1/7, 6.28318..., etc).

So if the initial number was 3.2 then the next multiples would be 6.4, 9.6, 12.8, etc