Over one's head

Meaning/Usage: When something is mentally too difficult to understand.

Explanation: To understand something, information needs to go inside the brain. This is used to say that the information failed to go inside.

I don't know the answer to that problem. The subject is over my head.

Don't bother explaining it to him. It's way over his head.

A:

I have to write a paper on the theory of relativity. Do you know anything about it?

B:

I won't be able to help you. The theory of relativity is way over my head.

Other Common Sentences

I don't understand the meaning. It might be too deep for me.

It's beyond my comprehension, so don't bother trying to explain it.