Am I thinking the right way?

There's good thought in this game. But on move 11, you said you played g3 with the intention to open up the h-file to cause problems if white castled kingside. This was not a good idea. Generally your opponent will actually want you to open up their h-file or a-file, because it gives them an open lane to attack you with their rook. In this position specifically, opening up your opponent's h-file allowed them to put their h-pawn in a more useful square closer to the centre, and to stare down a very vulnerable line in your position with their rook. So I would advise you not to allow your opponents to open the h- or a-files, especially when they haven't castled yet. Maybe instead look towards the g- or f-.

On move 18 when you traded bishops and were put in a queen and rook fork by white's knight, you said that it was worth it for the bishop trade, but I'm not sure that I understand why it was worth it. Instead of trading bishops immediately and losing material in the end, you probably could have forced your opponent's knight back with 15... a6, and then traded bishops afterwards to avoid the fork. But I see that you were trying to get rid of that bishop because it was in a very aggressive position.

On move 21 you seemed to miss that white was advancing their pawn to pin your knight to your king. You probably could have played Kg1 to prevent white from taking the knight.

Also, this one isn't a winning or losing decision or anything, but instead of playing Kf1 on move 30 to prevent checkmate, you could have instead played 30... Ne3+, forcing white to either put their king between their two rooks, thereby preventing checkmate, or to play Kg1, which puts them in a forced mate position.

Other than that, I think you had a good thought process throughout the game. Hope this helps.