Very enjoyable lesson, thank you!

I think attacking with the knight (to to D6 or E5) allows black to move his rook to F8, effectively defending the pawn. Attacking first by pushing whites pawn to F5 dislodges the bishop.... depending on blacks response, white can then capture the next pwn (covering the F8 square), or capture the bishop.... but the key is to dislodge that bishop from the same diagonal.

For the Puzzle at the end it would be Knight to E5, Bishop takes Rook, Knight to F7, Bishop takes knight (Forced) and then the second knight Mates by taking Bishop.

I'm just watching someone play a chess game by himself

For puzzle. Knight to D6 is a good flex. Rook takes the Knight - mate with our Rook to G8. If black, for example, takes our Rook, we check with a Knight takes F7, black is forced to take it with a bishop and we take with another Knight, which is a checkmate. That means, that black has to defend the pawn on F7 with it's Rook D8-F8 (D8-D7 is mate by Rook to G8). Wight has brilliant move Rook to C8. Black takes it with bishop or rook - pawns becomes too undefended and can be taken by our 2 knights.