White is doomed. Black's material advantage is overwhelming. Black wins by trading the pieces away. White's chances go away too. It will come down to Black's Q overpowering the White R, or the Black pawns running downfield to score a touchdown. If it's Black's move:
[title "Black to move"]
[fen "2k5/1pp2p2/p5p1/3b4/2NBq2P/1PK1N1r1/P7/3R4 b - - 0 1"]
1... Bxc4 2. bxc4 Rxe3 3. Bxe3 Qxe3+ 4. Rd3 Qe1+ (4... Qxd3 5. Kxd3 Kd7)
White has no immediate threats and can't really lose more material. So the exchanges are rather forced. The reason I recommend trading the pieces off here is that Black has a significant material advantage. Each even trade makes Black's remaining pieces relatively stronger. In addition, Black can create passed pawns on both sides of the board. Black can trade his Queen for the Rook and have an easy win that way, if he wishes.
If it is White's move, it isn't so easy because White has no moves. I can't really think of a good move.
1. Rd3 maybe. The only thing White has is a cheap-shot checkmate by
Bf6 followed by
Rd8#. It is unlikely Black will let him do it.
Regarding your other question, how could you figure this out, there's really no way except to try. You're on the right track when you count points and know Black is way up. After that, you examine the board and come up with a strategy. My strategy for this position is to trade pieces. So then I ask myself, "how can I do this?". The Bishop capture on
c4 was the first thing I saw. I realized he had to recapture, so he had 2 choices, pawn or King. If he used the pawn, I'd weaken his pawn structure even further - disconnected pawns are weak. So that was good. It's a combination of having a strategy, then looking for tactics to implement the strategy. When I see a poorly placed King and I have my Queen, I am trying to find forks everywhere. Or pawns that can't defend themselves. The
Qf2 queen move forks the
h pawns. One will drop. I am not too worried about White's Rook because if it gets too far from his King, I'll be able to grab it.