Here's a breakdown of the individual parts and how they could be used in different contexts:
* Oui je sais: This means "Yes, I know."
* Mais: This means "but."
* Aime bien: This means "likes" or "enjoys."
* Nan: This is a very informal way of saying "no" (short for "non").
Possible meanings based on context:
* "Oui je sais mais aime bien nan" could be a slangy way of saying "Yes, I know, but I like it anyway." This is assuming that "nan" is being used to express an opinion, possibly a playful disagreement with something that's already been established.
* "Oui je sais mais aime bien nan" could be a misheard phrase or a typo. There could be a missing word or two that would make the phrase grammatically correct and understandable.
To understand the true meaning, you need more context. Who said this phrase? What were they talking about?
If you can provide more information, I might be able to help you decipher the meaning.