"get off my back, will you!" whats the meaning?

Hi there..
could u tell me the meaning of this sentence.
and also this:

"The president cited his friend's telephone number off the top of his head"

what this sentence really means? I don't understand the meaning.

Thank you very much in advance!.

ANa LauRa...

[twostep]

Originally Posted by A. Laura

Hi there..
could u tell me the meaning of this sentence.
Leave me alone, do not bother me

and also this:

"The president cited his friend's telephone number off the top of his head"
Quoted the number from memory, did not have to look it up

what this sentence really means? I don't understand the meaning.

Thank you very much in advance!.

ANa LauRa...

Hope this helps