why my post’s full title not showing on google hompage?

Can you please elaborate on the issue?
WordPress does not control the length of the title on how it’s shown in Google’s SERP.

However there seems to be another issue with your site as the HTML validator is also not able to check your site and the inspector is throwing some errors(open browser inspector). Dubug by disabling all the plugins and see if it resolves the issue. You might also want to switch to a default theme to see if that resolves the issue. And when this is resolved, I suggest to install an SEO plugin that assists the appearance in the Search Engine.

I think google will only display 40 or 50 characters of a title. Your title exceeds that number. It just crops off what is past your title length. HTML allows up to 60 characters but google will not display all 60 characters.

Sir, google not show 40-50 words On display. Only 5-6 words show on Display. Is the reason i am used Hindi words in title?

Are you check my website filmik.in

Please solved This Problem

About the SERP length: https://moz.com/learn/seo/title-tag
Install Yoast SEO plugin as it comes with an SERP Tool.

But check your site for errors (see previous reply), because several online tools throw errors while trying to access your site. May be a plugin, may be something else.