How do I turn on Game Mode on my iPhone XR?

I use an iPhone Xr and noticed that when I enter the game It doesn't turn on "game mode". I have iOS version 18.4.1, the latest, but this mode is not in games. And it's not at the control centre either. This iPhone gives me my brother a few days ago. When my brother had this phone, it turned on this mode. After that, he reset the phone settings, and gave me, and I downloaded all the information from my old phone, and updated iOS to 18.4.1, it was a few days ago and I forgot that there is such a mode. Today I noticed that I don't have "game mode". Please help to decide, or if you know any information, whether it's a bug, if Apple knows about it, or you have the same problem, please write. I want to know that I'm not the only one who faced such a problem. Thank you in advance 🙏

[Re-Titled by Moderator]