You’re making progress if you realize that in this position you have to consider 1. Qe7+. Sure, it looks suicidal; after 1. …QxQ; 2. RxQ, KxR you would have given away a rook. But a less hurried view of the sequence is needed—and an application of the principle shown in the previous frame. After the first step, 1. Qe7+, QxQ, don’t mechanically imagine yourself recapturing Black’s queen. Pause and consider the board after just those steps, and see that Black’s queen would then be attacked once by your rook and protected just once—by Black’s king. A king is a poor guard for an enemy piece because an attack so easily drives it away. What checks would White have here? 2. BxB+. Black’s only legal move is to interpose his queen at e6; then White has 3. RxQ and has won a piece.

Another way to see this would be to observe from the start that White has the option of BxB+ and that only Black’s queen on d7 prevents it. Then look at your checks and see Qe7+, forking Black’s king and queen and requiring him to play QxQ. You realize that Black’s queen is overworked, and that after the sequence just described his bishop would be left loose. Giving up your queen to win the bishop wouldn't make sense, but then you see that BxB is a check that wins back your queen after all and leaves you a piece to the good.