How do you say in mandarin its been a long time?

There are several ways to say "it's been a long time" in Mandarin, depending on the context and level of formality:

Informal:

* 好久不见 (hǎo jiǔ bù jiàn): This is the most common and casual way to say "it's been a long time" and literally translates to "long time no see."

* 好久没见了 (hǎo jiǔ méi jiàn le): This is similar to the first phrase but adds the particle "le" which makes it slightly more formal.

Formal:

* 别来无恙 (bié lái wú yàng): This is a more formal and polite way to say "it's been a long time" and literally translates to "have you been well?"

* 久违了 (jiǔ wéi le): This phrase is less common but still a formal way to say "it's been a long time." It literally translates to "long time no see."

You can choose the phrase that best suits the situation and your relationship with the person you're speaking to.