How did the gentleman Gu Xiaoyan find out that Ren Dawei was cheating?

Gu Xiaoyan went to Gu Xiaozan and advised her sister to think of her parents, be responsible for herself and learn to find a man like Ren Dawei. Gu Xiaozan said that Ren Dawei is not necessarily a good person. When Gu Xiaoyan dug out the photos taken by the photographer arranged by Gu Xiaozan on Lele's birthday, she found David Ren's intimate behavior with Wang Sisi at home. Gu Xiaoyan was heartbroken. Gu Xiaoyan met Ren Dawei in the cafe and showed him the photos. When Ren Dawei saw the photos, he showed no remorse, in order to help Gu Xiaozan and Ouyang Jian keep Gu Xiaozan's secret from Gu Xiaoyan in front of their parents. Gu Xiaojun was furious, and Gu Xiaoyan, who was sitting behind David Ren, was extremely disappointed. Uninformed David Ren said in front of him that Gu Xiaoyan was too monotonous and unchangeable, but once. Gu Xiaoyan angrily splashed water on Ren Dawei's face and rushed out. Gu Xiaoyan asked Gu Xiaozan to keep secrets from her parents.