Justifiably declining. Being a pawn up is of no significance here.

White is trying very hard to bring back his rook to the scene of the action.

This lets White off the hook. More challenging was 37...Nf6 or 37...Ra2.

A lucky escape. Black does not manage to make anything of his extra pawn.

And the game ended in a draw a few moves later.

Improving the Pawn Structure
A queen exchange, like other exchanges, can also be used for positional gains, for instance, if it allows you to reunite pawns or undouble a pawn when recapturing.

30...Qg6 31.Bxd5 cxd5 32.Qc7 or 30...g6 31.b3 also leave White clearly on top.

A nice concept. White gives up his backward pawn on d4 in order to enclose the bishop on a8 .