Code working on Studio, but not on server. Using LocalScripts for this case is wrong?

Errors: Handle is not a member of tool (on the main script.) and Character is a nil value. (following script.)

Selection script: (localscript in playergui)

--[Locals]--
 
local player = game.Players.LocalPlayer
local character = player.Character
local mouse = player:GetMouse() --Getting the player's mouse
local folders = workspace.OreBlocks
local tool = script.Parent.Parent.Backpack:WaitForChild("Pickaxe")
local active = false
local humanoid = character.Humanoid

local selection = Instance.new("SelectionBox")
selection.Color3 = Color3.new(255,255,255)
selection.Parent = player.PlayerGui
selection.Name = ("PickaxeSelection")
selection.LineThickness = 0.09

--[Logic]--
 
mouse.Move:connect(function()
    if active and humanoid.Health == 100 then
        local target = mouse.Target
    
        if not target then 
            selection.Adornee = nil
        elseif target.Parent == folders then
            selection.Adornee = target
        else
            selection.Adornee = nil
        end 
    end

end)

tool.Equipped:connect(function()
    active = true
end)

tool.Unequipped:connect(function()
    active = false
	selection.Adornee = nil
end)

Main script: (localscript in my pickaxe tool)

--[Made by TheBoxofGhosts]--

--[Locals]--

local mouse = game.Players.LocalPlayer:GetMouse()
local tool = script.Parent
local sound = tool.Handle:WaitForChild("Sound")
local oresound = tool.Handle:WaitForChild("OreSound")
local selection = game.Players.LocalPlayer.PlayerGui:WaitForChild("PickaxeSelection")

--[Logic]--

local function onMining()
	if mouse.Target and mouse.Target.Name == ("DirtBlock") then
		sound:Play()
		script.Disabled = true
		selection.Color3 = Color3.new(0, 255, 0)
		mouse.Target:Destroy()
		wait(0.1)
		selection.Color3 = Color3.new(255, 255, 255)
		wait(0.2)
		script.Disabled = false
	end
end

tool.Activated:connect(onMining)

local function onMiningOre()
	if mouse.Target and mouse.Target.Name == ("CopperBlock") or mouse.Target and mouse.Target.Name == ("IronBlock") then
		oresound:Play()
		script.Disabled = true
		selection.Color3 = Color3.new(0, 255, 0)
		mouse.Target:Destroy()
		wait(0.1)
		selection.Color3 = Color3.new(255, 255, 255)
		wait(0.2)
		script.Disabled = false
	end
end

tool.Activated:connect(onMiningOre)