Do these sentences sound natural?

1.Giving me a reason that I should be concerned about what he has been doing.
2 They were semi forced to cheat in the exam. Especially that guy have been telling people that cheating in exams is not a big deal.
3. The teacher should watch out those students who are going to be cheating in the exam this time. Otherwise, other students won't take this course seriously. They wouldn't be studying if you allowed them to cheat.
4. I am not quiet too sure of what's the explicit name of the company that she has been working for. Maybe you should go and ask her about this.
5. If you come to know this very well, I believe you won't have to worry too much about this test.

1. Give me a reason why I should be concerned about what he was doing?

2. They were semi forced, or somewhat forced, to cheat on the exam, especially because that guy had been telling people that cheating on exams is no big deal.

3.  The teacher should watch out this time for those students who are going to be cheating on exam. 

4. I'm not quite sure of the name of the company that she's been working for, maybe, you should should go ask her.

5. If you know the information well I don't think you should be worried about the test.