It's a fine start, but I feel like your story is missing a couple of key ingredients:
1) The concept is fine, but flawed in some key ways. Unless you're an established writer, no one is going to want to make a high-budget monster disaster movie. It'll be too expensive. These movies tend to be heavy on spectacle, light on substance, and there's nothing wrong with that, but in order to get your foot in the door, you'll need to write a story that can function with a much lower budget. Not to mention, these are usually only made when there are established IPs behind them. They are not often original stories. Godzilla is an established franchise, Jurassic Park was a book first. That being said, characters fleeing monsters and disaster works as a genre, there just needs to be A LOT more substance than there usually is in these types of movies, ESPECIALLY from an unknown writer with an original story without an established IP. My favorite reference for you would be something like "Jurassic Park".
2) It needs a theme. Some sort of expressed moral value that the audience can wrestle with. In Jurassic Park, the theme is "don't mess with nature." The characters have a scene where they take the time to talk over the philosophical ramifications of the theme. They discuss and debate the theme. You characters don't need to do this as directly as they do in Jurassic Park, but it will definitely give your movie legs if they do.
3) You characters should have a "need." So far, all they have is a "want" which is to survive the monsters. Which is good, but in order for your characters to come alive, they also need a "need." This is something that's internal, as opposed to external. A flaw that endangers their lives, getting in the way of their "want" and only by conquering and finding what they "need" do they get what they "want." This is a commonly discussed element of storytelling, so if you're confused, a quick google search should clarify.
4) Research story structure. I felt like your story lost its legs by the end. Almost like you didn't know where it was going. If you want this story to get better, you need to get a beat sheet in front of you and fill it in. In other words, outline.
5) You had some really great witty pieces of dialogue scattered throughout in here! Do a LOT more of that. Try to fit one on every page (use discretion). Also, make sure you are not sacrificing characterization. Make sure it's something the character would actually say.
Theme and character needs are discussed regularly, so research these topics! I recommend the amazing series "The Anatomy of Chaos" on YouTube.
PRIORITIES:
1) Get an outline together. Make sure your story isn't undersized.
2) Establish the theme.
3) Establish your character's arcs. What is their "need"? How do they change before the end?
4) Add a LOT more punchy dialogue.
Thanks for sharing your story with me. Best of luck!
