What's the significance of the patrol dialogue in the teahouse?

In the second act of Teahouse, there is a dialogue between Lao Lin, Liu and Chen, in which the word "friendship" appears four times and twice contains subtext.

On one occasion, Lao Lin and Chen deliberately described their relationship very well, paving the way for the following. The second time, Lao Lin and Chen want to marry a woman. Lao Chen has a line, "The friendship of three people, no one laughs." Pockmarked Liu didn't understand the best context of this sentence, so he wouldn't understand the meaning of "friendship". Then there is Lao Lin's line "There is another girl", so Pockmarked Liu can infer Lao Lin's and Chen's intentions from the dialogue information.