Need help to create a save and load system to retrieve the players position
To save and load game states you should learn about the File class: https://docs.godotengine.org/en/3.1/classes/class_file.html Take variables from your nodes and write them to the file. Then to load, read the file and set back the variables in your nodes.
File
The documentation even has an example of how to save games: https://docs.godotengine.org/en/3.1/tutorials/io/saving_games.html
And similar questions were answered already: https://godotengine.org/qa/search?q=How+to+save