Download- Fydyw Tjss Ly Lhm Mharm Mn Tht Qb A... File

Given this is a puzzle, and you asked for a "write-up", I'd conclude the intended decoding is a (or 21 forward), yielding:

ROT-11: f→q, y→j, d→o, y→j, w→h → qjojh — no. Download- fydyw tjss ly lhm mharm mn tht qb a...

Let's brute force Caesar mentally:

But given the puzzle style and the phrase ending "... tht qb a..." — "tht" is likely "that" in plaintext if shift is constant. "tht" to "that" would mean cipher t→t (shift 0), h→h (shift 0), t→a? No, that's inconsistent. Given this is a puzzle, and you asked

Shift backward by 1 didn't work. Maybe shift forward? "tht" to "that" would mean cipher t→t (shift

Shift backward by 7: f(6)-7 = 25 → y, y(25)-7=18 → r, d(4)-7=23 → w, y(25)-7=18 → r, w(23)-7=16 → p → yrwrp — no.

Try right shift: f→g, y→u, d→f, y→u, w→e → gufue — no.