Nothing found

Pl. send in detail what you want?

or send your site detail then i see what problem and what you want?

Or

direct contact : https://socialcms.wordpress.com/contact-us/

my page: https://schluesseldienstpreisvergleich.de/

problem: https://schluesseldienstpreisvergleich.de/?s=magdeburg&cat=10
(Nothing found — their is no option to select a category)

I see https://schluesseldienstpreisvergleich.de/?s=magdeburg&cat=10 problem internal page you not add category wise search widget you currently add WordPress search widget in internal page add category wise search widget in internal pages

Its not an internal page. It is the nothing found page.

404.php/internal page not show category wise search widget therefore it not show if your theme option then add this widget.

you problem is theme related. add widget