Expressing “forget about it” with 别提了
We use the introductory phrase 别提了 
to express that we don't want to say something or continue a topic.
to express that we don't want to say something or continue a topic.Examples
别提了，真的，没什么事
Forget about it, really. It's okay
bié tí le, zhēn de, méi shénme shì
别提了，他骗了我好几次
Forget about it, he has deceived me many times
bié tí le, tā piàn le wǒ hǎo jǐ cì
Sometimes 别提了 can also be translated as “no need to say more”. We use it when agreeing with our interlocutor.
Examples
别提了，他就是个可鄙的懦夫
No need to say more, I know he's a despicable coward
bié tí le, tā jiù shì ge kěbǐ de nuòfū
别提了，她怎么敢这样做？
No need to say more, it’s terrible how she’d dare do such a thing?
bié tí le, tā zěnme gǎn zhèyàng zuò