My girlfriend and I lived in more than ten AirBNBs, most of them for minimum a month and this has been the best experience so far. The apartment is fantastic. It's a new building with new furniture and new equipment, so everything from the kitchen to the bathroom works perfectly. Especially the spacious bathroom with it's walk in shower stands out.
We lived in the apartment for half a year and we had enough storing space to put all our stuff in, which is often a problem in AirBNBs. Helmut also gave us access to the cellar so we could store our empty luggage.
The surrounding area is beautiful, you find a supermarket and a lot of small stores and coffee places around the corner and it's not far from the city center. Next to the flat is a Metro-stop and the Donaukanal, which is perfect to have a nice walk or a drink in summer.
The communication with Helmut and Monika went smoothly, at one point we accidentally broke the wardrobe stand, Helmut immediately brought us the one from his house and he refused to take any money for the one we broke.
My personal recommendation for you is to buy some bread, sparkling wine and cheese from the cheese-shop around the corner and enjoy it on the big balcony.