I stayed at Gudruns apartment with my cousin for three nights and we had an awesome stay! The apartment is very well located, even bigger than it seems in pictures and super clean - everything we could wish for. The only thing to note if you are a light sleeper is that the bell of the nearby church starts at 7am and you can hear it to the apartment. It didn't bother us though.
Gudrun and her husband Armin were very fast and thorough at replying to my messages before and during our trip and we could check-in straight from airport - they gave very good guidance for how to get to the apartment (the airport bus was really convenient, arriving very close to the apartment). We could also arrange a later check-out.
All in all, we felt warmly welcomed and would stay definitely again. Highly recommend!