Issues with creating Audit Log

Trying to edit our Audit Log in our Policies Table that will show who edited the file, what the file said before and what it's changed to now. We are currently using Dynamic Form Rules on our current Audit Log (Text - Multi Line) Field:



What the Audit Log Field is currently set to:




But what we really want is something that tells us that anytime the Policy is modified we see who made the change, what it was set as and what it is now. I did look into setting up an automation, but I couldn't get it to work.