when i run full crawl it completed within very short time 20 seconds and searchable items are 0, and users unable to search the site.

In search server event viewer i found below errors 1. The start address cannot be crawled.

Context: Application 'Search_Service_Application', Catalog 'Portal_Content'

Details: An unrecognized HTTP response was received when attempting to crawl this item. Verify whether the item can be accessed using your browser. (0x80041204) our site is running on https

and second error i found

Gatherer\CSS connector failed to connect to CSS net.tcp:///ContentProcessingComponent1/ContentSubmissionServices/content

sharepoint search topology:

1 Search servers has all components except query components

in two wfe : query processing components.

Make sure your content access account has read permission on all the content databases.

End result isn't bad but there's a few steps first:

• Check that the crawl account is listed with read permissions in a web application policy.
• Test that you can view content running IE as the crawl account on the crawl server