Translation of vernünftig

I really worry about the health of obese people, especially the ones that I know in person (friends, relatives), because it is well known that overweight have a higher probability of heart attack.
We had time to walk around the waterfall but refrained from entering the little lake at the bottom. My fellow tourtakers were quiet nice and we spend a while just sitting in the grass near the water.
The travel agent's representative promised that they would return us the difference of the money. They also assured us that we would get special treatment, such as extra drinks and a Kayak expedition.