Corrected sentence: In dry grasslands, you'll find few trees and few mountains. There is very little shelter, and all you can hear are the rustling grass and the whistling wind.
Notes (simple explanation):
- "You'll" is short for "you will" and is fine to use in this sentence.
- "Few trees and few mountains" means there are not many of them. That phrase is correct.
- "There is very little shelter" is correct because "shelter" is treated as one idea (something you can hide in).
- For the part about sounds, "all you can hear are the rustling grass and the whistling wind" matches the two things you hear (grass and wind). Some people also say "all you can hear is..." and that sounds fine in everyday speech.
Very simple version for a 6-year-old: Dry grasslands have few trees and little shelter. You can hear the grass rustle and the wind whistle.