Hi @mertozsoy
Thanks for providing that information.
It looks like for this URL https://teknikmi.com/lenovo-p2-ekran-degisimi-orijnal-lcd-ekran/, you’ve set it as a FAQPage, but are indeed not using the Yoast FAQ block (which is needed to add the appropriate markup).
In order to resolve this, you can either set the schema setting back to ‘WebPage’ or add the Yoast FAQ block – https://yoast.com/features/structured-data-blocks/
If you add the Yoast FAQ block, we would expect that it would add the correct and missing ‘mainEntity’ markup, and you would then be able to validate the fix in Google Search Console after.