Please send your website URL and WordPress admin login details at firstname.lastname@example.org along with the text which you want to translate in default contact form. We will surely solve all of your problems.
You can also translate the contact form fields by editing custom-functions.php file
Go to the custom-functions.php file which is inside the inc folder of your theme directory
at line no. 714 find the function for contact form
so you can change the contact form fields and messages.