von Scheve - Teichmann, Berlin 1907

Lichess: https://lichess.org/study/DVIX3vFT/dMmDL5SF

One bad move here are 9 h3, it opens up the pawn for a sacrifice in which you take the pawn for a bishop, breaking open the king's space, you also can take another pawn later with Qg3+ followed by Qh3.

Another bad move was exchaning the knights on move 10. That weakens the kingside even more, basically removing your knight from the defence and black still has a piece there.