Yippee! That was the right hint, @Pedro! I had to tell Windows via the NVidia control panel to use the graphics card. Now I can see something inside the game! But now to the next problem: The picture is only displayed correctly if I choose a resolution of 640x480. But I would like a resolution of 3000x2000. If I set this resolution, the picture is too big, so that it doesn't fit on the screen.
That is an odd resolution. Are you sure it’s correct? It’s not even a standard aspect ratio. It’s only been tested with 4:3 and 16:9. Have you tried other resolutions with a standard aspect ratio?
make sure that full screen is selected and compare with your monitors native resolution, you can manually set the dimensions in the file OpenGL.cfg if the launcher is giving you false values.