I've many hard nuts to crack, do you have any?

A hard nut to crack

The meaning is –Someone or something that is difficult to understand, solve, or deal with.

Similar idioms –

• Tough cookie

• A puzzle

Examples

1. That math problem is a hard nut to crack—I’ve been stuck on it for hours.

2. She’s nice, but a bit reserved. Definitely a hard nut to crack.

中文意思是 – 難以對付或理解的人／事 / 难以对付或理解的人／事