Translated version I used below:
thank you very much for your answer but I did not understand everything because I am still starting.
I'm sending you what I did to find out how the spikes I placed can cause my character to go back to the start.
Thank you again for your help.
While I understand starting out and not knowing everything, I would highly suggest learning more about Godot and game development, and creating the solution yourself. This is because, while I could program it for you (at least in theory), it will not be tailored to your game and, most importantly, you will not know how it works. This means it will be much harder to fix if there is an issue and customize to your game if requirements change. Another reason to program it yourself is that game development is hard, and learning how to program solutions to fundamental problems will serve you well later! Small prototypes and problems solved in seemingly unrelated projects has served me really well when I encounter strange problems in projects, so I would not discredit learning.
I would highly recommend going through some Godot tutorials, especially those that seem similar to the game you are wanting to create. Most tutorials also have the source code for the project shown in the tutorial available for download, so you can look at the code and see how they accomplished the mechanics shown.
Also, the code you send does not have anything in it for detecting spikes, though it does have code for detecting gems. If the code for spikes is similar to the code for gems, then the following snippets should help give you an idea of how to move the player to the start (though I still would highly recommend going through some Godot tutorials for the reasons above):
# The starting position
var starting_position = Vector2.ZERO
func _ready():
# store the starting position in a global variable
starting_position = global_position
func _on_Spike_area_entered(area):
# go back to the start!
global_position = starting_position
