I want the screen to "zoom out" when the character moves fast. How do I do this?

FieldOfView is a property of the Camera.

local Players = game:GetService('Players')

local Camera = workspace.CurrentCamera
local Player = Players.LocalPlayer

local Character = Player.Character or Player.CharacterAdded:Wait()

local runningSpeed = 30

while true do
    wait(.1)
    local humanoidRootPart = Character:FindFirstChild('HumanoidRootPart')
    if humanoidRootPart then
        local hrpVelocity = humanoidRootPart.Velocity.magnitude
        if hrpVelocity > runningSpeed then
            Camera.FieldOfView = 90 -- zooms out camera
        else
            Camera.FieldOfView = 70 -- default view
        end -- speed check
    end -- a check for base part, we're using this to detect how fast a player is moving
end -- while true do

You can also use TweenService as a way to smoothly move the camera in/out between walking and running.

There is a property of the camera called FieldOfView this property is a value (which means number of any kind)

To change the FOV you must write this in a local script

local Camera = workspace.Camera

while true do
if --[[vehicle speed variable/directory goes here]] >= --[[the normal speed of the vehicle in numbers goes here]] then
Camera.FieldOfView.Value = 90 --you can put a different value this is just what I am doing
wait(0.1)
end

please tell me if I made any mistakes, I hope this helped!