I would say "Campeonato de LFS". No doubts here
About the process, yes, I know what you mean. If you compare it with the English string it's quite clear.
Every time I think whether it should be "de" or "del" for the Spanish translation I come up with something different
One could mean that there is another LFS.exe process running and the other that there is another LFS-related process running, but not necessarily LFS.exe
"Otra ventana de LFS" and "Otra ventana del LFS" means the same for me as LFS runs only one window/process at a time. But if, for example, LFS opened a different window to see the replays then the warning would be "Otra ventana de LFS" and not "Otra ventana del LFS" because it's not the same window.
In the current situation I would accept both "de" and "del" as correct, but maybe that's just me and I'm wrong, but I cannot see where
I think you could use either "de" or "del" and nobody would really notice the difference
Greetings