Choose the most appropriate preposition for each gap.

I love skiing. I have been practicing this sport at least 15 years and I still enjoy it.
Standing on the skis and going downhill all weathers has turned me an experienced sportsman. Whenever I am part a ski- and snowboard-group I usually find myself a leading position. Sometimes even experienced athletes left me the leadership role due to my competence to navigate the map. I just need few seconds to look a map and I know exactly what to do. It is easy me to estimate when and were the sun goes down, where the best views and easy or difficult slopes are. Furthermore, I always find nice places to rest and eat lunch. first these aspects seemed to be very easy to deal , but if you are in a big group and there are both good skiers and very good ones, i.e. so called the experts, you often have to be very flexible and very well organized. Organisation is essential this role due to the closing times the ski lifts and bus timetables. If you are late and you are in a wrong valley with a group or even alone, it is very expensive to come back to your hotel. Image how much you might have to pay a 100-km-taxi drive one person is to get home to your hotel. This is why most people finish their ski-days much earlier than I do. The last lift is always my last ride. That’s why everybody is satisfied when they go skiing with: They always get an intensive programme any further costs.
Last year I was skiing with a group in St. Johann, and there was a student who knew everything better than the others. So, he became the leader, and we were keen finding out if he was really as good as he was saying. It was a very nice day, but in the end he didn’t calculate the time correctly. So, we had to go for least two hours up the hill. During this walk it got dark and our leader got depressed. That was when I realized how important my organisational skills are, and therefore I’m going to get my skiing instructor qualifications next autumn.