You ain't flex anything lol.
Then I discussed it with my friends and they ask me to cash out but I refused then Sassuolo turned the game around and Score two goals.
Read the sentence you wrote, this mean your friend already know you bet on Sassuolo, so it doesn't surprise him.
What should be flex is when you didn't tell him if you bet Sassuolo in the first place and you show if you win or you win a lot of money.
If it's just a common bets e.g. betting tiny amount on big underdog or betting on favorite, it's not something that make people will respect you.