My hobby.
My hobby is
mountain climbingClimbing is very exciting and interesting.
I've been to Mt.Kinabalu in Malaysia.
The mountain is Height of 4095 meters high.
I went there alone. Then I got altitude sickness. It was scary for me.
But I can climb up the mountain! It's my valuable experience.
NOt sure what you want to convey here --
But I climbed to the top of the mountain!
I learned I could climb such a high mountain.
What's the "it" in the valuable experience.
Climbing this mountain was a valuable experience?
sometines "valuable experience" means you learned a lesson.
Going up the mountain by myself was a valuable experience, because I learned never to go mountain climbing alone.