Thanks so much for sharing your writing. It's great to see people take an interest in writing, and find that it's an exciting and stimulating thing to do! Kudos to you for putting yourself out there.
I read through your prompted writing assignment and I think it's a fine start. I like the way you unfold your story and I like the overall nonlinear structure. It's interesting and I think most readers would be interested to hear more about the world where your story takes place.
Having said that, there's some real work to do here. I've provided a few notes below to help you get your story structure a little tighter and improve your storytelling skills.
You need to work on breaking up your text. It's hard on your readers when you present them with a wall of text, and it's especially hard when the story is giving us multiple voices talking (to each other) along with action sequences. It's just hard for the eyes and hard for the brain. You make your readers spend too much energy trying to keep their place and keep the characters straight, instead of focusing on your story.
As a general rule, when the focus of your narrative shifts and/or when your focus character shifts, you should start a new paragraph. As an example, let's look at your last paragraph. You wrote:
Her eyes opened, finally. It had been one hour, thirty two minutes and sixteen seconds since the helicopter had stopped rolling. Jason formed a smile. “Wake up Aliza.” She looked at him, in a half daze. “Jason, what? where are we?” As she looked around she could still see the great wall, but it was dark and she was on the wrong side of it.
But this would be so much easier to read if you did it this way:
Her eyes opened, finally. It had been one hour, thirty two minutes and sixteen seconds since the helicopter had stopped rolling.
Jason formed a smile. “Wake up Aliza.”
She looked at him, in a half daze. “Jason, what? where are we?” As she looked around she could still see the great wall, but it was dark and she was on the wrong side of it.
Splitting that one paragraph into three saves the user from having to figure out what's going on and/or who is saying what. In your last paragraph there's not so much to make sense of (so it's easier for the reader); but in your larger walls of text, it's particularly hard on the reader to keep their place.
You need to work on the way you tell your story. There's some structure in your story that's really weak, lacking a better way to say it. Your sentence structure sometimes isn't conducive to the sort of action/adventure you're trying to convey. You should use action verbs where you can - let your verbs do the work for you. Show me what happens instead of telling me about it. Not sure what I mean? Here's a good example. You say:
In the background a distant persistent wailing could be heard.
But you don't want to tell me about what was going on in the background, do you? Your action here is all tied up in the verb "to be". You can do better. You did do better. In this sentence. You talk about a "distant persistent wailing", but you don't make it your action; you waste it as the subject of your sentence. Try this quick-and-dirty rewrite:
Sirens wailed persistently in the distance, it was all she could hear.
I'm not saying this re-write is perfect or anything, but do you see what I did? I made the action of the sirens foremost. Sirens wailed. That's a marked improvement, don't you think, over wailing could be heard.
Proofread. If you want others to enjoy your writing as much as you enjoy writing it, you've got to spend a little more time proofreading (or asking a friend to proofread) before you share it. There are some obvious things here that should have been spotted before you shared this; and -- if you did -- it would be easier for your readers to enjoy your story. A few examples:
OK, that's enough to get you started. You're already doing one of the two easiest ways to make yourself a better writer. You're reading. The other thing to do is just to write. And then keep writing. And then write some more. Keep writing. Seriously. Good luck.