How do you make a gui show up when you touch (Not Click) a brick?

So you can achieve this with the Instance.Touched event, however, the server cannot access individual player's guis from a server script, so that must be done locally. Luckily local scripts can detect Touched events of items in workspace, so that helps you do this without the use of a remote event/ remote function.

The goals of the local script should be to : 1) have a touched event 2) check if a body part of the player is touching the part 3) if so, make a GUI pop up

so, here it is

--it should be a LOCAL SCRIPT (putting this here to avoid confusion)
local player = game.Players.LocalPlayer
workspace.Part.Touched:Connect(function(hit)
    if hit and hit.Parent then
        local plr = game.Player:GetPlayerFromCharacter(hit.Parent) 
        if plr and plr == player then
            --player.PlayerGui.ScreenGui.Frame.Visible = true
            player.PlayerGui.ScreenGui.Frame.Visible = not player.PlayerGui.ScreenGui.Frame.Visible
        end
    end
end)

Now what this script does is checks if the thing that touched the part exists and has a parent. If it does exist and has a parent, the script then checks if that part is the player character and if it is, then it checks if it is the local player, which is definable from local script, then if all of that checks out, it turns the visible property of the frame to true or false

rubenkan version

--it should be a LOCAL SCRIPT (putting this here to avoid confusion)
local player = game.Players.LocalPlayer
workspace.Part.Touched:Connect(function(hit)
    if hit:IsDescendantOf(player.Character)
        --player.PlayerGui.ScreenGui.Frame.Visible = true   
    end
end)