Practicing "Phrasal Verbs."

1- The guard went off like a shotgun when he heard the thief. 

This would mean that the guard lost his temper and became very angry when he heard the thief. If you mean that the guard shot at the thief with his shotgun, you could say "The guard started blasting away with his shotgun when he heard the thief"

2- I'm going off to make a Skype group to practice speaking skills.
3- My students are going off to a party to celebrate the student's day.
4- When I wake up in the morning I go in and look at my trees.
5- The nurse will join a voluntary group in Iraq. 
6- I had to set off early to avoid the traffic.
7- The policeman set off the alarm on   in the mall.
8- Scientifics  Scientists found out a cure for the zika virus. 
9- I would will find out the real reason why some women doesn't don't want to take contraceptive pills.
10- I was going to enrol in at the driving school but something came up and I couldn't.

Practicing "Phrasal Verbs."

1- The guard went off a shotgun when he heard to the thief.  Like the other commentator, I do not understand what you mean, but I think it is this sentence: The guard shot his gun when he heard the thief.
2- I'm going off to make a Skype group for practice speaking skills.
3- My students are going off to a party to celebrate the student's day.
4- When I wake up in the morning, I go in look at my trees. I look at my trees when I wake up in the morning.
5- The nurse will go in of a volunteers group in Irak The nurse will be in a volunteers group in Iraq.
6- I had to set off early for avoid the traffic. I had to leave early in order to avoid traffic.
7- The policeman set off the alarm on in the mall. The policeman set off the alarm in the mall.
8- Scientifics found out a cure for the Zika virus. 
9- I will ould find out the real reason why some women do not want to take contraceptive pills. In this example is best to use do not or dont'
10- I was going to enroll in the driving school's but something come up and I couldn't.

Great Job Nicole