My favorite sport - climb monutain

Mountain-climbing is the kind of sport I like most. Last summer, I joined a climbing club whose main activities are organizing this type of outdoor activities. In fact, mountain-climbing is a good physical exercise. Due to stressful the stress of life in Beijing, I hardly have spare time to do exercise on weekdays. So I usually do some outdoor activities with my friends on weekends. There are a lot of mountains in on the outskirts of this city. Actually, if you go to any of these mountains, you might meet a lot of young people. The air quality in the mountain areas tends much better than in downtown areas. This is why so many people want to escape from their dwellers city dwellings and arrive there to breath fresh air.
Of course, sometimes this sport can be physically demanding. In other words, you should make sure you are strong enough to climbing climb peaks before doing it. In fact, this could be dangerous to people's health.

For verbs: after "to," you always need to use the infinitive (basic, or dictionary) form of the verb. So you can't ever say "to climbing," but must say "to climb." This is basic rule that you can always apply when writing or speaking.