Beginner here, and I have no idea how to fix this
For some reason there’s a problem on my PlayerMovement script
How do I solve this?

None of the above matters.
The answer is always the same… ALWAYS!
How to fix a NullReferenceException error
https://forum.unity.com/threads/how-to-fix-a-nullreferenceexception-error.1230297/
Three steps to success: