Do you mean the Sinfonia to Bach's Cantata 156? I've just checked the original score to be sure, and I would say that the version posted on August 17th already contains the whole sinfonia. After that there's an aria for soprano, tenor, strings and continuo. Of course, please correct me if I'm wrong.

Maybe I was wrong asking for the sinfonia, and I should have said cantata.
Actually I'm not sure about what melody was talking my teacher; we played the "Dolce" by Telemann, and she could have referred to the other sonatas.
I should ask her next week and I'tell you.

Thanks again four your great job.