Small follow up after my first try with v0.6:
Most of the bugs I encountered in v0.6 are gone with latest fix version 0.6.1. But I had to start from the beginning.
I still encountered some errors, but a click on ignore worked and I was able to play to current end without bigger issues.
I think at least one of those errors is related to items I already had while I shouldn't be able to have them at that moment.
That's for the massage oil. I was able to ask for translation before I actually had the erotic massage book, resulting in being able to get the oil before I even got the quest. At the moment I got the oil, I also got an error (click on ignore worked for me and as I used it after I got the corresponding questline, no further problems showed up with it).
The walktrough (huge thanks for it!) helped a lot and is quite accurate. Besides oiling the bedroom door (worked at 5), I only noticed some minor differences. One of them was that I wasn't able to get the erotic massage book in the shop at the moment mentioned in the walkthrough. Two days later after the first massage I got the quest for it and with that the book appeared in the store.
It might be helpful to actually follow the walkthrough as exact as possible - don't get items too early even if available in shop, don't use dialog options (like the one asking for translation help) if not mentioned in the walkthrough for that moment.
Addition: as I see many questions regarding problems with blackmailing Derek - don't mistake him with Dick! You have to get more than only one shot at the bedroom ;-)