Answer 1

Speed is not the same as speed.
Python is case-sensitive. It is convention to use lower case for variables. Class names are Capitalized, snake_case is preferred for compound words...

so it should be:

speed = 740

if also needs the ':' at the end

if speed >= 500:

also Slow down! needs to be enclosed in " " to be a proper string.

print("Slow down!")

elif needs a condition, so something like:

elif speed>200: