Of course people walk at different rates, but in checking out the walk from First to Bachalpsee and back I am seeing walk times ranging from 40 to 90 minutes each way! It's hard to plan around that.
We're 60+ but pretty good walkers. Our usual pace that makes Google's city-street estimates fairly accurate. I'll stop for photos but let's leave that part out for now. And we would NOT walk around the lake(s).
How long really?