i asked from google forum…they replied about this language indexing like this:
" Thanks for the reply.
Thanks for presenting the screenshots.
I took a look at it and I don’t think the “tell Google about the localized version of the page” method is communicated correctly!
I am not getting any hreflang errors, but I wasn’t sure if using the x-default value was correct in this case.
(x-default is used when the user’s browser settings do not match other languages or regions specified.)
I think the result is that pages with /de are normalized to pages without /de.
If the site is in only two languages, English and German, the x-default value seems unnecessary.
Try using these to modify your site and successfully tell Google about each version!"