processor exclude words option does not work

If you search for only a stop word, then you either get all content as results or none (could depend on backend plugin or other configuration). If the former is the case, then it is expected that content containing the word “des” will also be shown.

I expect you’re using the database backend for searching? Then the partial matching option is in the search server settings.

Does this resolve your problem? Otherwise, please provide more details.

i do use the database backend for searching, and i cannot see that "partial matching option".

Could u tell me the url and screen capture ?

Simply click on “Edit” for the search server (admin/config/search/search-api/server/[SERVER_ID]/edit and it’s there. See screenshot.

what if it s not there ?
i cannot see it ( see capture)

Simply click on “Edit” for the search server (admin/config/search/search-api/server/[SERVER_ID]/edit) and it’s there.
In your case, click on “Data server” in the Search API overview.