Can anyone help me with this gui?

I'd advise you to name your objects something that isn't very similar to common properties, such as "Name" and "Text". Name is a property of ALL DataModel objects in ROBLOX. Bad naming convention!

You also have to keep in mind that if you edit a GUI in StarterGui, it won't apply to any player before they respawn and get the updated GUI inserted into their PlayerGui. You want to change the GUI in the PlayerGui!

You can do this several ways, and I'll show you two of them. The first is the use of player:GetMouse() and Mouse.Target to track what you're hovering your mouse over. This requires a LocalScript, but since you're editing GUIs you'd need that anyway.

local Player = game.Players.LocalPlayer
local Mouse = Player:GetMouse()
local target = game.Workspace["Apple Tree"]
local label = Player.PlayerGui.NameBox.NameGui.Text

Mouse.Move:connect(function()
-- Checking if the target actually exists, and checks if the target is a descendant (child, direct or indirect) of our 'target'
    if Mouse.Target and Mouse.Target:IsDescendantOf(target) then
        label.Text = target.Name
    else
        label.Text = ""
    end
end)

The second method is to actually use the ClickDetector. This requires the player to physically click on the tree, though - else the ClickDetector-event won't fire. I don't suggest using this method, as every player will require to bind the event.

local Player = game.Players.LocalPlayer
local Mouse = Player:GetMouse()
local target = game.Workspace["Apple Tree"]
local label = Player.PlayerGui.NameBox.NameGui.Text

target.ClickDetector.Clicked:connect(function())
    label.Text = "Apple Tree"
end)

Well first of all, you don't want to use a ClickDetector. You should use Mouse.Target to do this. You would need a LocalScript inside the TextLabel. Insert this code:

local Mouse=game.Players.LocalPlayer:GetMouse() --Gets the players Mouse
function Mouse.Move:connect(function(Property) --Fires each time a property of the Mouse is changed
        if game.Workspace.AppleTree:FindFirstChild(Mouse.Target)~=nil then --Checks if the Mouse is hovering over the target or not (You may need to adjust this to fit the apple trees actual name...whatever it is)
            script.Parent.Visible=true --shows text if Mouse is over tree
        else
            script.Parent.Visible=false --removes text if Mouse isn't over tree
        end
    end
end)

If you have any further questions or complications, leave a comment below addressing the issue. Hope I helped :P