Could You Plz Gime Explanatioan About Ever And Never

I'll begin, but wait for other explanations...

NEVER is negative, it means "not + ever" (opposite to "always"). You don't use "not" in a sentence with "never", because it's already in it:
I never wash my hair on a Sunday
I've never seen such a thing!

EVER is positive, means "once (in your life)
Have you ever seen a thing like this?
If I ever go to New York I'll send you a post card

And then you have the expression "for ever (and ever)", which means "for all eternity"

I agree with YoungCalifornian.

Here is what Cambridge online dic. tells :

Definition ever (AT ANY TIME) [Show phonetics] adverb at any time: Nothing ever happens here in the evenings. Have you ever been to London?

I see. I mistook your intended meaning of "once" to be 'one single time.'