Local scripts only works once caues i don't know what is the reason , HELP ?

local tool = script.Parent
local player = game:GetService("Players").LocalPlayer
local oGUI = script:FindFirstChild("ScreenGui")
local db = false


tool.Equipped:Connect(function(mouse)
    local GUI = oGUI:Clone()
GUI.Parent = player.PlayerGui
    wait(1)
    GUI.Equiping.Visible = false

    mouse.Button1Down:connect(function()
    if not db == true then
        db = true

        local ray = Ray.new(tool.Glowstone.CFrame.p, (mouse.Hit.p - tool.Glowstone.CFrame.p).unit * 400)
        local part, position = workspace:FindPartOnRay(ray, player.Character, false, true)
        local beam = Instance.new("Part",workspace)
        beam.FormFactor = "Custom"
        beam.Material = "Ice"
        beam.BrickColor = BrickColor.new("Cyan")
        beam.CanCollide = false
        beam.Anchored = true
        beam.Transparency = 0.15
        beam.Locked = true
        local distance = (tool.Glowstone.CFrame.p - position).magnitude
        beam.Size = Vector3.new(0.3 , 0.3 , distance)
        beam.CFrame = CFrame.new(tool.Glowstone.CFrame.p, position) * CFrame.new(0,0, -distance /2)
        game:GetService("Debris"):AddItem(beam, 0.1)
        if part then

            local human = part.Parent:FindFirstChild("Humanoid")
            if not human then
                human = part.Parent.Parent:FindFirstChild("Humanoid")
                end
            if human then

               human:TakeDamage(3)
               human.WalkSpeed = 1
               wait(1)
               GUI.Time.Visible = true
               GUI.Time.Text = "4"
               wait(1)
               GUI.Time.Text = "3"
               wait(1)
               GUI.Time.Text = "2"
               wait(1)
               GUI.Time.Text = "1"
               wait(1)
               GUI.Time.Visible = false
        wait(5)
        db = false
        end
            end
        end
    end)
end)


	

This is a local script and when i click my mouse it only shoots once

Your issue is that you only check if the value of db is false once, and once you check if it is false, you set it to true. The only time you would set it back to false, according to the code you provided, would be if you hit a player. I would recommend changing your script to this:

local tool = script.Parent
local player = game:GetService("Players").LocalPlayer
local oGUI = script:FindFirstChild("ScreenGui")
local db = false


tool.Equipped:Connect(function(mouse)
    local GUI = oGUI:Clone()
	GUI.Parent = player.PlayerGui
    wait(1)
    GUI.Equiping.Visible = false
    mouse.Button1Down:connect(function()
    	if not db == true then
        	db = true
	        local ray = Ray.new(tool.Glowstone.CFrame.p, (mouse.Hit.p - tool.Glowstone.CFrame.p).unit * 400)
	        local part, position = workspace:FindPartOnRay(ray, player.Character, false, true)
	        local beam = Instance.new("Part",workspace)
	        beam.FormFactor = "Custom"
	        beam.Material = "Ice"
	        beam.BrickColor = BrickColor.new("Cyan")
	        beam.CanCollide = false
	        beam.Anchored = true
	        beam.Transparency = 0.15
	        beam.Locked = true
	        local distance = (tool.Glowstone.CFrame.p - position).magnitude
	        beam.Size = Vector3.new(0.3 , 0.3 , distance)
	        beam.CFrame = CFrame.new(tool.Glowstone.CFrame.p, position) * CFrame.new(0,0, -distance /2)
	        game:GetService("Debris"):AddItem(beam, 0.1)
	        if part then
	            local human = part.Parent:FindFirstChild("Humanoid")
	            if not human then
	                human = part.Parent.Parent:FindFirstChild("Humanoid")
	            end
	            if human then
	               human:TakeDamage(3)
	               human.WalkSpeed = 1
	               wait(1)
	               GUI.Time.Visible = true
	               GUI.Time.Text = "4"
	               wait(1)
	               GUI.Time.Text = "3"
	               wait(1)
	               GUI.Time.Text = "2"
	               wait(1)
	               GUI.Time.Text = "1"
	               wait(1)
	               GUI.Time.Visible = false
	        		wait(5)
	        		db = false
	        	end
        	end
		else -- You were missing this
			mouse.Button1Up:Connect(function()
				db = false
			end)
        end
    end)
end)