Multilingual, which structure to choose?

Question

Search Engine Optimization

Hello.

Website: catalog, aggregator
2 languages ​​(Russian, English)

Approximately 30% of offers will be in Russian and will not be translated into English, the remaining 70% will be in Russian and English.

Is there any logic in building such a structure:
site.com/ru/offer-page (adding the ru slug), if the same page does not exist in English?
Or do so? site.com/offer-page/?hl=ru Could you tell me

which multilingual structure is better to use in my case?

Answer 1

site.com/ru/offer-page - I use this one in my projects.
No page - 404.
Moreover, I am additionally making a request to site.com/offer-page with a 301 redirect depending on the browser language [lng]. If there is no such page, then go to the main site.com/[lng].
Although, it is possible and better: go up the section one level higher until the section in the selected language is available and display the message: "There is no such offer and you have been redirected to the nearest section in your language" (or indicate additionally: in which languages, it is present to allow the user to select, navigate and read in another language).