Australian backpackers may have dependence issues; Israeli IT dudes are chill as fuck; Swiss-German Ph.D students may be too gossipy and can play the game of chess very well. German dudes may not be willing to explain that the Swiss-Germans were talking about me. Riding a bike in Amsterdam is the best attraction. Stopping at local coffee shops allows you to see the diversity of the city. Amnesia is the best shop in Amsterdam. There is a line between not knowing and not willing to be wrong. I may be paranoid. The words I hear and slight suggestions from the Swiss Germans matched with their behavior and my assumptions—but you will never really know. It is better to be safe than sorry. You could have gone with it and everything would have been fine, but it was up to forces beyond your control. The only thing you can do is try because every missed opportunity is a lost one.
Take your time, if you wish to say something to the group, start with one person and the others will tune in accordingly.
Trip with Swiss-Germans was an interesting experience. I did not fully know what their intentions were except to keep their friends safe. Subtle moves can go a long way. Keep your distance.