What should I do if my wife cheats on me? (Sexual knowledge adult novel)

My wife and I have been married for several years. We have a good relationship and a great sex life. But last year, after my wife went to a kindergarten with foreign teachers, she kept asking me some strange questions, such as "Is the black one very big?" At first I didn't pay much attention to it, but later when I saw photos of their unit traveling, I found that there was a black teacher, so I asked her, "Do you have black teachers in your unit?" She said yes! The black man was very humorous and could speak Chinese very well. I don't care. Later, no one knew what happened to the black teacher, and he returned to his country. Until last week. My wife went out and forgot to close QQ, so I found out that they had a one-night stand. I spent 5 hours watching the whole thing and found out that they only did it once. My wife also said, "Your DD is 20 centimeters." These were some of the things they reminisced about afterwards. From their conversation, I knew that my wife still loved me, she was just curious and wanted to try black people. At the same time oral sex everything. The black man also played with my wife's anus with his fingers. They did it twice more during the day. And my wife said it took so long that she almost felt dizzy. He also said that my wife is very good at playing and is the most fun he has ever had. But when I think back to when I had sex with my wife, her vagina never felt loose! Wouldn’t it be loosened up by a big cock? I'm so depressed now. Is this a divorce? Just pretend you don’t know. These days I have been fantasizing about my wife having sex with him in a perverted way. Can anyone give me some advice on what I should do now?
This has been edited after the moderator reminded me, thank you.
I also want to ask what I should do, should I pretend I don't know or divorce her? She treats me very well now.