user27368: Black (me) to move.
I took the knight at f3 with my knight at e1. However, Lichess analysis shows that this move is a blunder, and suggests to take the bishop at g2 instead.
IMO, I am winning no matter I exchange the knight or bishop, but I feel hard to understand why exchanging the knight f3 is a blunder?
[FEN "r1bq1rk1/pp3ppp/4p3/2Pp4/2P5/P1B2NP1/3NPPBP/R3nRK1 b - - 0 1"]

1...Nxf3? (1...Nxg2!)


user4418: 
why exchanging the knight f3 is a blunder?

It obviously isn't a blunder.
I suspect you've made the mistake of thinking that if the website tells you that it evaluates Nxf3 as fractionally lower than Nxg2 then that means that Nxf3 is a blunder. It isn't. A blunder is when your large positive advantage turns negative. A blunder loses you the game from a roughly equal position or throws away a winning advantage. It is not when the evaluation changes slightly against you.

27368: <p>Black (me) to move.</p>
<p>I took the knight at f3 with my knight at e1. However, Lichess analysis shows that this move is a blunder, and suggests to take the bishop at g2 instead.</p>
<p>IMO, I am winning no matter I exchange the knight or bishop, but I feel hard to understand why exchanging the knight f3 is a blunder?</p>
<pre><code>[FEN &quot;r1bq1rk1/pp3ppp/4p3/2Pp4/2P5/P1B2NP1/3NPPBP/R3nRK1 b - - 0 1&quot;]

1...Nxf3? (1...Nxg2!)
</code></pre>
 4418: <blockquote>
<p>why exchanging the knight f3 is a blunder?</p>
</blockquote>
<p>It obviously isn't a blunder.</p>
<p>I suspect you've made the mistake of thinking that if the website tells you that it evaluates Nxf3 as fractionally lower than Nxg2 then that means that Nxf3 is a blunder. It isn't. A blunder is when your large positive advantage turns negative. A blunder loses you the game from a roughly equal position or throws away a winning advantage. It is not when the evaluation changes slightly against you.</p>
