I entered the correct code, but an error appears and does not run. NameError: name 'speed' is not defined.

Python beginners make a lot of mistakes.

Clear or rename the turtle.py file on your desktop.

The reason for the error is

from turtle import *

The error NameError: name 'speed' is not defined occurs because the turtle package in the library is not imported in part, the turtle.py file is imported in the same location as the script, and speed is not defined in the turtle.py file.