People are making me depressed and their words putting a phobia of death on me. I know everyone must die but if someone is supposed to die tomorrow,he will die today just by thinking this. So please help me and give me appropriate reply whether someone negative words or prayers regarding life span get accepted or not?

You should not be worry at all. There are millions Muslims living in the Western countries and thousand are extremely strong in their faith than any Asian and Muslims country.

The most important thing regarding any believer is his/her strong faith in Allah. If your faith is strong nothing will defeat you.

The Holy Quran says:

الَّذِينَ آمَنُوا وَتَطْمَئِنُّ قُلُوبُهُم بِذِكْرِ اللَّهِ أَلَا بِذِكْرِ اللَّهِ تَطْمَئِنُّ الْقُلُوبُ

Those who believe, and whose hearts find their rest in the remembrance of God – for, verily, in the remembrance of God [men's] hearts do find their rest-:

So the only thing which can give you peace and tranquillity is the remembrance of Allah (swt).

It’s Allah favor upon humans that we don’t know what would happen in near future. Or we don’t have knowledge of Unseen. Therefore please don’t pay attention what people are saying.

At last don’t think negative. Life and death is in the authority of Allah and what you are eating and doing, as in your actions, are in your authority. Human being is the best creation of Allah and Allah has given infinite power to the Human so he can manage and tackle any situation in his life.
May Allah ease your ways and protect you from all evil powers.
One kind recommendation if you offer you Salat on time you will overcome everthing Inshallah in your life.