Explain why the regular expression does not work?

Question

Nginx

Here it works correctly And here it says that the page is not present.
rewrite ^/ru/(.*)?$ /$1;

rewrite ^/(ru|es|de|fr|pl|tr|it|nl|pt|ja)/(.*)?$ /$1;

Answer 1

Because the numbering has shifted and instead of `$1` you need to write `$2`

Answer 2

If you do not need a language, then you can try:
if the language is needed, then your code is needed, but it will already be $1, and everything after it is $2, as they wrote before me