Im wondering, how did yuyang and qui know each other? Also, how do Qui know about Lihuan's love for Yuyang

The ran into each other in chapter 90. He overheard a conversation between him and the uncle and then the uncle explained to him that YuYang dumped someone because he's not gay.
However, that's all there is and it was never shown that he knows about YuYang's past or his mental state.