Julia has been very friendly and gave us useful pieces of advice . She also offered us coffe and thea every day. The area where she live is 20 minutes from the center using tram and underground (the public transport works very well:tram every 5-7 minutes and the stop in 1 minute walking from the flat). In about 8 minutes of tram you will be in one of the most important station where you can take train, metro, pullman and other tram.
Besides this, there was a nice view from the terrace and the flat was very very clean: we really appreciate it!
With wi-fi it would have been perfect but you can go in a cafè and use the internet there. In conclusion I really reccomend such a lovely flat in Vienna.