Has the usual Intel HD Graphics 4000 and there is NO upgrade for the hardware.

The Intel HD Graphics 4000 is not for gamers. You can improve performance slightly with the known answers so I'll list them here and hopefully other folk can add more.

1. Try VirtuMVP.
2. Try it with maximum RAM (8GB) Link:
3. Set all games to lower settings. Less pixels, turn off sound tracks, effects.