Everything was great!
Martha was waiting for us at the given address and gave us the keys. She was there to answer to all of our questions and made us feel comfortable.
The place was really nice and clean.
It is near the Naschmarkt in a quiet neighborhood.
The metro station is 5 min away but there is no need to take the metro for Hofburg Palace, the Opera or Karlskirche because you can go there by feet too (it takes around 15-20 min)
Super, I recommend it!!