Thanks for you response.
I have exactly done what you have explained to create lang file in my package at first glance but its not seems to be working so that's why I have changed the admin lang file.
Yes I can explain it and here is the explanation for the same.
I have created 3 custom packages and used them into yours' "Admin" and "Shop" package. But I didn't made any changes to your packages(Webkul Packages) for lang file update.
Then I had noticed that in admin all labels are not come from lang file.
Then I had made changes to admin lang file by overriding webkul admin package and then its working for my package and as well as in Webkul package.
Also one more thing that I have notice that If I remove lang file from my package, its not working and layout seen like this screenshot : .
Thanks and Regards,