How to write a multilingual string class?

Question

OOP

How to write a simple and fast string class that can support most languages?

Requirements:
- you can not use standard and third-party libraries.
- speed and simplicity.
- the possibility of assignment and addition.

If there is quality material on the link - I will read it with pleasure.

Answer 1

In fact, the work plan is quite simple: look at how existing popular solutions are made and do it in the same way.
This solution will be able to answer all points, except for the expediency of creating a bicycle, if this is not a term paper or a thesis for education.