I think rainforests are very hot and humid. But rainforests are beautiful and cool, because sunset is very nice. I think rainforests is mysterious, so I want to go to the rainforests in the future.

Here's another edited essay, Jimmy! Please note how I removed the comma before the word "because". You don't need a comma in that sentence. Also, take note of how I changed the expression "I think" to "I believe". They are similar so you can use them interchangeably. Have a good night there and see you tomorrow! 

Cheers,

Jean~~

                     What do you think of rainforests?

I think rainforests are very hot and humid.

>> CORRECT~~

But rainforests are beautiful and cool, because sunset is very nice.

>> But rainforests are beautiful and cool because the sunset is very nice.

I think rainforests is mysterious, so I want to go to the rainforests in the future.

>> I believe rainforests are mysterious so I want to go to some of them in the future.