Is there any documentation that you are following?
Lot of forum but cant find the solution or why does not work. In the past we always made 2 headers (1 for each language) but that looks like is not possible anymore. String translation just dont show the translation. The menu "works"
as I can see from your debug, I assume you are building header via Elementor templates. In that case, you should not use string translation to translate Elementor content.
Please try to follow the next guide and translate your header template via Translation Management:
Well tried all. We duplicate all but looks like i got it working again with duplicate. The header & footer was not possible to duplicate so tried string. (thought that this always will work)
The suggested way is just to complex and lot of extra work. (this is reason why we always duplicate)