1. They don’t know how much is important understand about the healthy.
2. He would like meet some people every day, but with de racing rotine in his life, it becames almost impossible.
3. We have the internal procedure which describes best pratices to create a good relationship at job.
4. There is a possibility , the company where he works change to another city.
5. Everyone does part of terrible accident what happened yesterday.

1. 
In illegal conversation(also natural) :
They don't know how is important understanding about health
Legal:
They don't know how important understanding about health is. 

2. He would like to meet some people everyday, but with the racing routine in his life, it becomes almost impossible. (corrections: to meet; the racing routine; it becomes.) 

3. We have an internal procedure* (if you didn't talk about what is your procedure before whom you tell this, you should use a/an articles) 

4. There is a possibility that, the company where he works(or he works with) can(or will) move to another city. 

5. Everyone is part of the terrible accident that happened yesterday. (corrections: is; the - because, whom you talk they already know this; that.)




Suggestions are welcome to improve the naturalness