Its a custom function made to turn the character blue. You can ignore it (forgot to delete it).
Math Expressions are worth digging into. It will save you a lot of space and ease the math visually. You can even type the name of the variable and it will automatically add it.
Here are some links:
Delete this:
Makes no sense to give it the value it already has.
That Note should be saying that the cast should always pass since you are getting the CharacterMovementComponent and casting to it aswell.
You could save yourself that cast and assign value directly to the variable, but IMO you should still check for a null pointer (or expect it to eventually crash if owner doesn’t have one). Changing the cast to a IsValid should serve the same purpose. There is no harm leaving it as is at least until you get it all working.
Just be patient and keep at it. Feel free to post if you need anything.