The flat was perfectly located for me : 5 minutes walk from the Messe north entrance. The perfect place to stay if you are at Berlin for an event taking place at the Messe.
The closest subway station is also less than 5 minutes walk.
The flat is very clean, nice, quiet. Everything you need is there.
The Wi-Fi internet works perfecly.
Heike was very nice and very helpful. She gave good advice about what restaurants to go to and what to see.
If I need to go back to Berlin for the same event, I definitely will contact Heike before anyone else.
To be recommanded with no hesitation.