To bark up the wrong tree means to waste one’s efforts by pursuing the wrong thing or path.

For example:

If you think I’ll help you cheat, you’re definitely barking up the wrong tree!

I barked up the wrong tree when I applied to such good colleges with my average grades.

I’m not going to help you with your homework. You’re barking up the wrong tree.

I have been trying to solve this math problem for 30 minutes, but I think I’ve been barking up the wrong tree.

They are barking up the wrong tree when they bring their protest to this Parliament, which has no responsibility for decisions like that.

Jason was barking up the wrong tree when he said I was the one who ate the last of the cookies.

Tradução:

Bark up the wrong tree significa “desperdiçar tempo” com algo que não lhe trará resultados ou de enganar-se por “acusar a pessoa errada”.

Exemplos:

I’m not going to help you with your homework, Bob. You’re barking up the wrong tree.

Eu não irei te ajudar com seu dever de casa, Bob. Você está desperdiçando seu tempo.

If you think I’m guilty, you’re barking up the wrong tree.

Se você acha que eu sou culpado, você está acusando a pessoa errada.