Can you correct my writing?

The customer wants me to translate his language and both make a subtitle file format and a copy in formal file format of translation version. But I want to reject the subtitle file format politely so I wrote an answer below. Can you correct my writing if anything sounds unnaturally?

Thank you for sending the message! Sadly, I think I can work on only a copy in normal file format.

If you are okay with it, you can take the option Premium($35) and please tell me if you want the translated version to sound formal or informal!