Some Url Path Doesn't Work (When There Is No Php Extension File)

Maybe somebody good at with Nginx , php configs. I can't figure out what's wrong

When I click on categories or sign in links where the full url is only consisting of paths(no php extension) it can't find the path.

In error log it says -> "/var/www/html/" is not found

The root is okay here is the place where I have index.php init/php etc. But why does it look for this path here and why it adds index.html ?

I would appreciate any help