I’ve installed Fedora 39 on my computer, but when I play a game, after about 20/30 minutes the system locks up and forces me to do a hard boot, without any error being displayed. Can anyone help?
More infos please 
What does “running a game” mean? Is it a linux game, what software do you use? What GPU do you have, what drivers do you use etc.
You can use this to find relevant packages
rpm -qa | grep APPNAME
Or use the settings page “system” to get the info.
Also what error message should be displayed where? Poorly not many apps display their own error messages. Try to reproduce this and before open a terminal and enter this:
journalctl -f --priority warning