Sentence translate Quesion
But a new study finds that there's another group of adolescents who are in nearly as much danger of
the same psychiatric symptoms: teens who use tons of media, don't get enough sleep and have a sedentarylifestyle.

1. what's the meaning of experiencing ？

2. what's the meaning of ' in nearly as much danger of '? //means more and more close danger ?

Question

Sentence translate Quesion
But a new study finds that there's another group of adolescents who are in nearly as much danger of 
the same psychiatric symptoms: teens who use tons of media, don't get enough sleep and have a sedentarylifestyle.

1. what's the meaning of experiencing ？

2. what's  the meaning of ' in nearly as much danger of  '?      //means more and more close danger ?

Answer

In this sentence you could substitute "experiencing" with "having". 
To experience the symptoms is to have them or to suffer from them. 
"In nearly as much danger of" means to be in "almost the same amount of danger as". 
 I am guessing that earlier in the paragraph or article it talked about another group also.