What would be a good way to add custom translations for an unsupported language?

I would like to add a language setting to my game that includes a few extra languages that aren’t officially supported by Roblox, as well as the ones that are.
I’ve noticed that in the official supported languages (with configure localization), the strings say "{number1}" for some texts. For example: "Upgrades: ({number1}/{number2})"

Currently with the translation system I made, it doesn’t do this, meaning it’s not possible to make more accurate translations. So far, the way I’ve done it is to make it use string.gsub() for the string and :

I think that to achieve the {number1} {number2} {… solution, I could use string.gsub(), but I don’t know a way to do this that accounts for 2, 3, 4, … digit numbers.

If you know any way to achieve this, or even an idea please tell me!

For anyone who finds this 2 years in the futute, this is still not the full answer, but it’ll get you closer.

Another link to help: String Patterns

I hope this helps someone eventually!