I'm not afraid of dying, because I believe I'll be with God and my loved ones. What I fear is, how I'm going to die. There are so many horrible ways that people die. Some people die in tornados, in car accidents (which can be painful), in bombs, wars, and so many other disturbing manners. I'm also afraid of how my loved one's might die, and that I might witness these horrible events. I can't even watch horror movies because of nightmares. I pray about it, but the fear is always there. How can I get over this?

Unless you are convicted of a heinous crime in a state with the death penalty and multiple available means of execution... or commit suicide (considered a mortal sin in most religions) you generally have no control over how you will die. So why waste energy and time worrying about things you have no influence over.

Person who is born will die one day. Everyone knows it. It is the concept that you should accept it as soon as possible.
Live your life positively without worrying about how you or your loved one will die.

But by the way death is not painfull. When you'll die you will not feel it. Its just that your heart will stop beating.

You should not be afraid of dying it is normale. You should like the idear and do something that is fun and stop thinking about it b-coz it will take over your life when the time come to die you will die a great man once said "when your times up, your times is up". Fear not for death but for the after life for you don't now what your going to face in it. Death is apart of life you just need to inbrace it

This may help a little, but it means correcting what you said:
1. You aren't afraid of DEATH, but you are afraid of DYING. This is actually common and very understandable. Who wants to die some painful way?
2. Live your life in as good a way as you can, being careful, but not so careful that you don't enjoy it.
3. Work at being as healthy as you can. Of course genetics and accident can squash that, but the idea is to do what you can. (I didn't, and suffer pain in my late 60s, from things like high blood pressure.)
4. Look around you at people who have a terminal illness. Most of them accept it, and are at peace with it, as long as they aren't in pain.
5. If you have your sight, hearing, all 4 limbs, and are not limited in any way, be glad. Many don't. Someday you might not. Take advantage of what you have, while you have it.
6. On the societal level, be aware of the laws of various countries around the world. More and more of them are accepting 'right to die' laws, so that people don't have to suffer, and some countries even allow assisted suicide for any reason. Some states in the US allow it for those with terminal illness.

As for sudden catastrophes? One would be fine with me, just a few seconds of dying, when endorphins kick in and keep you from suffering too much, and then you are gone.

I know that death is scary, when I was little I used to cry for hours, just scared of how I will die. The thing that I slowly learned is that if you are scared of death your whole life, then were you really living? I know this might not make sense but that is how I thought of it.

Death is death. In most of those, your body is shut down, and after death, you will not beware or suffering anyway.

Bombs, war ( unless you live in a war zone) those are unlikely. Most more likely to die from a health issue at old age.