Dear Alper, 

thank you for your message. Unfortunately, for the time being the Turkish language is not envisaged for either the Help Center or the user guide. You can, anyway, request it by writing a post about this issue and setting it as an "Idea" . In this way, our developers will consider the possibility of adding this language. 

As far as the control panel is concerned, your customers should be able to acess it by using your admin username and password. Still, it is still not possible for them to change or update the project, as it is necessary to own the software in order to modify the website. 

I thank you for your understanding. Kind regards.