Guimaraes has played just five times for Lyon since his €20million January move from Athletico Paranaense, but the 22-year-old has already made his Champions League bow against Juventus.
The clash gave the Brazilian the chance to face Ronaldo, a five-time Ballon d'Or winner.
Guimaraes came out on top, too, playing the full 90 minutes as Lyon claimed a 1-0 first-leg lead in the last 16, with the return match yet to be played due to the coronavirus pandemic.
Ronaldo is "a guy I used to play with on video games", Guimaraes said.
"We talked in the game in Portuguese," the Lyon man said. "He said it was not a foul, and I said it was a foul.
"I was going to ask him to swap shirts with him, but he was kind of angry. He's a guy who doesn't like to lose. This is what we have to take as an example; a guy who has won everything [but] hates to lose.
"I want more and more to have this in my mind, being able to get the good things from these football legends, which is super important."
Discussing his nerves ahead of the match, Guimaraes said: "I was very nervous and slept badly at night because it was my first Champions League game, as a starter and in the last 16.
"But I thought to myself: 'If I want to be a great player, this has to be normal in my life. I have to play well against these guys.'
"I was very focused and I felt like I was playing on the street. Obviously, you are nervous to go on the field and when you are out there you get butterflies.
"But when the ball rolls, everything is normal. It's 11 against 11."