Проблему решил, вот код, если кому то нужно
TObjectIterator< APlayerController > ThePC;
UWorld* TheWorld = ThePC->GetWorld();
AFPSGM* MyGM = Cast<AFPSGM>(UGameplayStatics::GetGameMode(TheWorld));
if (MyGM != NULL)
{
MyGM->Health += 50;
if (MyGM->Health > MyGM->MaxHealth)
{
MyGM->Health = 100;
}
}