How to I make a button that changes the player's walkspeed when clicked?

What you need: Local script / Normal script / Remote Event / GUI

In The frame put the local script and a button Edit the button name in the local script provided below

put in local script:

script.Parent.Button.MouseButton1Click:Connect(function() -- Edit button to your buttons Name
    game.ReplicatedStorage.ChangeWalkSpeed:FireServer(50)
end)

Create a remote event and name it "ChangeWalkSpeed" and put it in ReplicatedStorage

Create a script and put it in ServerScriptService and add this code:

game.ReplicatedStorage.ChangeWalkSpeed.OnServerEvent:Connect(function(player, Speed)
    player.Character.Humanoid.WalkSpeed = tonumber(Speed)
end)

Tell me if it works!

Edit: Had two errors in local script just fixed

In local script (That's in the Button)

local Speed = 0 -- change this to the number of speed you want


script.Parent.MouseButton1Click:Connect(function()
    game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = (Speed)
end)

Haven't tested so idk if it'll work

Also if your making when you equip a pet, you should have it to when the pet is equipped it'll have a passive boost of speed. (To prevent people from getting speed by just clicking the button)

If it is a local script, here is what you do:

local button = script.Parent
button.MouseButton1Click:connect:(function()
game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = (Your speed)
end)

Accept answer if I was useful! Any questions? Add me! MedMike#2018