The file you mentioned above has nothing to do with translation. The instruction for translating Dokan can be found here – http://docs.wedevs.com/translate-dokan-plugin/. Please read this carefully hope your problem will solve otherwise let me know.
I know this, but the string I still see in English is not in the dokan.pot file.
Maybe there is not the latest one in your contribution?
An example: Store list -> visit store -> contact form: “This field is required.”
Sorry about replying late. I tried to edit the form-validate,js file from your plugin editor. But it was not available to download.
If you can provide the FTP access, I can try again to fix that for you. You can mail me your FTP credentials at sekander[at]wedevs.com