Two New Doors

Grandma ordered (ordered as in purchased, or ordered someone to do something?) to build two new doors in our house. A neighbor warned her,”Building a new door means a person will die in this house.”
Grandma didn’t give a shit (know your audience before you use this word, could be considered offensive to some people); however, and grandma and grandpa were diagnosed with fatal diseases in the same year, both cancer.
“Block the two doors,” said grandma, in the final moments of her life.
The story made me scared. What if I do something that causes my death? This thought haunted me for a while, then I realized that the death of my grandparents was meant to happen. The two new doors were just the signals. They are not the reason.

Two New Doors

Grandma ordered to build two new doors built in our house. A neighbor warned her,”Building a new door means a person will die in this house.”
Grandma didn’t give a shit still wanted the doors, so she had them built anyway. however, That same year, grandma and grandpa had were diagnosed with fatal diseases at the same year, both cancer.
“Block the two doors,” said grandma, at the final moments of her life.
The story made me This incident scared me. What if I do something that can cause my death. This thought had haunted me for a while, but then I realize that the death of my grandparents was were meant to be happen. The two new doors were just the signals. They are not the reason.

the death of my grandparents: you should remove the "of my grandparents" before deciding if the following verb should be was or were.  "the death was meant to happen".  In this phrase, the subject is not grandparents, but is death which singular.  If you write "the deaths of my grandparents", then you can use "were".