But if it’s a Caesar shift of -1 for whole phrase: b→a, y→x, h→g, s→r, s→r → “axgrr” — not matching.

Better approach: Maybe they encoded English words by shifting each letter by +1, but the phrase “Download-” is plaintext. Then “byhss” shifted back 1 → “axgrr” — nonsense.

Given the complexity, I’ll guess the puzzle’s completion is likely:

Let’s instead guess the plaintext language is Arabic in Latin script, cipher is ROT1 (A→B). Then to decode, shift back 1: