t→r, h→g, m→n, y→t, l→k → r g n t k → rgn tk not right. Try one key right: t→y, h→j, m→, (comma?), no.

t (20) +13 = 33 mod26 = 7 → g h (8) +13 = 21 → u m (13) +13 = 26 → z y (25) +13 = 38 mod26 = 12 → l l (12) +13 = 25 → y

Maybe it’s a simple ROT13 (shift 13):

Thmyl Lbt Rzdnt Ayfl Ly Ppsspp -

t→r, h→g, m→n, y→t, l→k → r g n t k → rgn tk not right. Try one key right: t→y, h→j, m→, (comma?), no.

t (20) +13 = 33 mod26 = 7 → g h (8) +13 = 21 → u m (13) +13 = 26 → z y (25) +13 = 38 mod26 = 12 → l l (12) +13 = 25 → y

Maybe it’s a simple ROT13 (shift 13):