Rabt Thmyl Bwt Fry Fayr Here

becomes:

If I decode the message "rabt thmyl bwt fry fayr" using a simple Caesar cipher, I get: rabt thmyl bwt fry fayr

"RABT THMYL BWT FRY FAYR"

It looks like you're using a substitution cipher, specifically a letter substitution where each letter is replaced by a different letter a fixed number of positions down the alphabet. becomes: If I decode the message "rabt thmyl