Was ist der Unterschied zwischen again und anymore ?Du kannst auch einfach Beispielsätze geben.

I think this is a followup to my previous answer, so let me explain:

I will never have a relationship with her again: I had a relationship, now I don't, I won't have another relationship with her. The relationship ended, so you don't use "anymore" in this sentence. You say "again" because you would be starting a new/second relationship.

Other examples:
I'll never do that again.
You should never go there again.
He asked me the same question again.
(All of these are completed actions and you are talking about repeating the action.)

I don't have a relationship with her anymore/We're not in a relationship anymore: I had a relationship but now I don't. Anymore is used here to indicate that it existed before but now it doesn't. You're not talking about what will happen in the future, only saying that your previous relationship is over.

I don't want anything to do with her anymore: Same idea as above. I wanted to know her in the past, now I don't.

Examples:
I don't like peanut butter anymore. (I used to like it, now I don't.)
He doesn't want to go anymore. (He wanted to go, now he doesn't.)
They aren't fun anymore. (They used to be fun, now they're not.)