MaxMana is not a valid member of ScreenGui?

The error is at the if statement Can someone please tell me how to fix this? its not finding the int value even though it exist in the gui!

game:GetService("UserInputService").InputBegan:connect(function(inputObject, gameProcessedEvent)
    if inputObject.KeyCode == Enum.KeyCode.E then
        if script.Parent.Equip.Value == true and SlashCool == false and ManaGui.MaxMana.Value > 0 then
            if ManaGui.MaxMana.Value > 20 then
                SlashCool = true
                ReFol.RSKILL:FireServer()
                ManaGui.MaxMana.Value = ManaGui.MaxMana.Value - 20
                wait(5)
                SlashCool = false
            else
                    ManaGui.ManaEn.Visible = true
                    ManaGui.ManaFrame.Frame.TextLabel.Text = "Not Enough Mana"
                    wait(.3)
                    ManaGui.ManaEn.Visible = false
                    ManaGui.ManaFrame.Frame.TextLabel.Text = "Mana"
            end
        end
    end
end)

EDIT:when you die and respawn it will says that it cant find maxMana