Dear Madam, Sir,
Upon reviewing your job proposal, I realized it was something I was accustomed to doing. I currently work as an English and French online teacher and I have been providing translation work in both languages in the past. I'd be more than happy to translate your documents from English to French and vice-versa.
How many words are there in total? What is the content of the document? Is there a software you would like me to use in particular?
I work efficiently, meaning that I am organised and, thus, provide quality work while respecting the deadline.
I am looking forward to working with you.
Bets regards.