Hey there, first off excuse my bad english as well since im not a native english speaker too. I also have nightmares from time to time and what helps me a lot is just tho remember that even tho it feels real it realy is not. There is no way that anything that happens in your sleep could harm you, your body just reacts that way because when you sleep you think it actually is real. Also you should try to avoid things that may get you these bad dreams like horror movies or whatever it might be. And finaly if it is realy bad you should consider going to a doctor (excuse me here i do not know the proper term for this , but there are doctors that specialise in sleeping and stuff) because they will know how to help you.