Dear Sir or Madam,
I am a German and English tutor and can correct grammar, orthography / spelling and punctuation in German. I'm quite skilled at spotting the mistakes and correcting them, having been confronted with such texts by my students on a daily basis.
The 15 days deadline is fair enough in my opinion.
It would be also nice to know, what kind of text it is.
Are we talking about a translation text?
Feel free to contact me through the chat option.
Kind regards,
Maria L.