Is 'quick' instead of 'fast' really wrong?
Absolutely not. Report it.
@DennisVanBeek - As an antonym to ”slow”, ”fast" is more suitable. For comparison see: "quick answer, quick visit, quick mind, etc vs. "fast man, fast car", etc.
Would "lent" mean the same as "încet"?
Good question! I sort of think about lent for slow and incet for quiet, but I can be wrong.