"I'm so glad I found another person" - input on my short story

I have been writing this story for English class and would love some input on what i should add to this story. I don't want it to make it a sappy story either. Also sorry for the grammar errors i haven't

perfected it yet.

The last man on earth sat alone in his room, silently staring into space. Not knowing what to do after realzing he may be the only person alive. He lived in a small town in kentucky and was attending a university . He was a young man in his early 20s who was an exceptionally smart man who knew a catastrophic even was going to unfold.

Apparently, the russians were angry with america after siding with the country they hated most and was planning to start World War 3 in Russia. Result of that Russia had sent 2,000 atomic bombs our way. In return america sent 3,000.

After realising what may happened Jason built a bomb shelter in his basement. He was constantly telling his friends to build one but they were skeptical and said told him "There wont ever be a nuclear war and it cost too much too build." His shelter was stocked with necesitys to survive for 5 years. He had everything from ramen noodles to his own garden of fresh vegetables. His parents thought he was crazy for building such a thing because they were just like his friends and told him, "That type of event is never going to happen there is nothing to worry about."

So here he was the last man on earth, not knowing what to do, sitting, wondering, and asking why no one but him has survived. While wandering around his shelter he suddenly hears someone yelling, "Hello!? Is anyone here?" Jason thought he was just hearing things but after it got louder and closer he heard a knock on the door. For a second he thought he really was going crazy but then it came again and again. then came a reassuring scared female voice,

"Is anyone there? Please, anyone?"
Jason stood behind the door hesitating if he should open.
"Oh please let someone be here! I am unable to find any other survivors" the girl sobs.
Jason opens the door.
"Oh! Thank God!" Shouts the young lady as she hugs Jason. The hug came so fast that it caught him off guard.
Jason is still baffled not know if this was real life or not. He has not been out of shelter much because he has been alone for 2 months and previously searched for 3 weeks and found no signs of life.

She says, "I'm so glad I found another person I thought I was the only person left! I have been searching for the last 2 weeks and noticed the sign you had put up."

A different approach or suggestion just to get you started. I'm not the best in grammar either so please overlook my errors.
I cannot describe how I knew that what I was doing was the right thing to do, I just knew. I remembered what people thought of me, how they ridiculed me as if I was eccentric. The look on the contractors face when I approached him, his head slowly tilting sideways while his eyebrows crunched inwards. "Are you serious" he said. I remember the neighbors protesting the endless convoys of steel and cement trucks tearing potholes in the streets, and lines of inspectors conducting countless surveys and reports. My parents, they would constantly try to pursue my idea, to invest in the future instead of wasting everything on an unbelievable anticipation of thing to come. My sweet sister Carla; she was about as innocent and brilliant as they come. She was a graduate in environmental and marine science, and was on expedition in the Gulf of Mexico when it happened. There was little warning, just a ten minute notice broadcasted over the emergency network. The Ham radio just keep on looping while saying; "attention all citizens of North America, turn of all electrical equipment and go to your basements until further notice." That was it; it just kept on repeating over and over again. Then they hit. It sounded as though standing directly behind a turbine engine of a jumbo-jet, bellowing a deafening whistle that shrieked through my ears. A shock wave hit a rolled over the ground like a tsunami destroying all it contacted, and almost collapsed my lungs and oral cavities as it passed overhead. I remembered seeing blinding light bounce back off the heavy metallic exterior door as I closed it while scampering inside, the great locks supporting the ten ton door clicked close, and that was it. My life underground had begun.

Click. That noise, what was it? Suddenly everything became cold and I covered up. Then, the smell of moss entered my nostril so rich I could taste it. Was this still a dream? My eyes opened and I looked around for a minute while realizing the air pressure change. "The doors are open." I said out-loud...

From here, all you have to do is develop Jason's character, and send him on a quest in search for his sister. Maybe she is on a similar mission to reunite. Place Jason's setting in the west shore and his sisters in the East. Describe the trip in detail including what the blast zone looks like (plants, wildlife, etc.). Have them meet in between. On his trip you should provide a description of Jason and his sister, and details of the inside workings of his bunker along with a brief description of the armageddon. Good luck.