Hmm how to make a setting where a user types a number and the fov will be that number

code: let me know if I need to change something

local FOV = workspace.Camera.FieldOfView

if script.Parent.Text == tonumber(FOV) then
	workspace.Camera.FieldOfView = nil
end

Put this as a direct child of the textbox

local TextBox = script.Parent
local cam = workspace.Camera

TextBox.Changed:Connect(function()
      local number = to number(TextBox.Text)
      if number then
           cam.FieldOfView = number
      end
end)

A better solution to this problem would be to set up and event that only fires when the user actually presses the enter key. This can be accomplished using the FocusLost event for TextBox.

local Camera = workspace.CurrentCamera
local default = 70

TextBox.FocusLost:Connect(function(enter, input)
  local value = tonumber(TextBox.Text) or default
  Camera.FieldOfView = value
  TextBox.Text = value
end)

The parameters include a boolean for if the enter key was actually pressed, and the input that caused focus to be lost. If you want to use these you can, but I stuck with a simple code for example purposes.