Blob1349 When trying to download a game that I really wanna play, it installs I try to open it but it closes instantly.
This is most likely due to one of the Exploit protections/mitigations that GrapheneOS has such as Hardened memory allocator, Memory tagging, Native code debugging, Dynamic code loading via memory, or Dynamic code loading via storage.
Go to Settings > Security and privacy > More security and privacy > Notify about system process crashes > toggle ON and you when you launch the app again it should show you a notification about the cause of the app crash.
If it was due to any of those Exploit protections, you can either disable them one by one or disabling them all for that specific app by pressing and holding on the app icon > selecting App info > scrolling to Exploit protection compatibility mode > toggle ON and then force stopping the app and relaunching to see if it will launch the app without crashing.