Hello Jaydip Patil,
I've checked this behavior on my test environment. Please let me explain, the pre-selected language of this "Insert Template" dialog is not related to the language of the customers contact.
The pre-selected language is the language, your or the CRM User has set within the language UI options for the CRM environment itself.
For example, if your UI language is set to English, you will see by default the english templates:
If you switch your language to German, for example, you will see the german email templates selected by default:
As this is an internal dialog, there is unfortunately also no way, to change the default pre-selected language programatically.
But as the idea, to have the email-templates pre-selected by the preferred language of the related contact record, is very good, you can suggest these kind of idea within our Ideas page, at https://experience.dynamics.com/ideas/
Here you can suggest new features and changes, which other users can up-vote. The Product Group will have a look at these in a regular way and this idea will have the chance, to be part of one of any future related CRM version.
I hope, with this information I was able to help you for more clarification and your ask about this behavior is resolved.
Otherwise, please let me know, if I understood anything wrong at your question.
Thank you very much and have a nice day.
