add minimize/fullscreen/close buttons

Why does this compile but the game doesn’t start in fullscreen.
Added a gamemode c++ class:

#include “MyGameMode.h”

void AMyGameMode::BeginPlay()
{
if(GEngine)
{
UGameUserSettings* MyGameSettings = GEngine->GetGameUserSettings();
MyGameSettings->SetFullscreenMode(EWindowMode::Fullscreen);
MyGameSettings->ApplySettings(true);
}
}

Thanks