The picture seems to be working with a short cable but also with FullHD via VGA. At 1920x1080 and similar resolutions you should try to take HDMI anyway. Since there are affordable cable with 5 and I think also 10 meters.
Also silhouettes of another review here I do not recognize. Silhouettes can make himself by hanging two or more VGA cable in succession. Pro Another cable a shadow / edge comes more. There may be sloppy produced copies of the adapter where something occurs, but my was not among them. Then you can test whether the connections with their own strengths.
For image problems, I would take other cable and first test with shorter / better cable. Adapter from VGA to HDMI, there is also lying, perhaps, but at 30 euros.
With Bluetooth or wireless mice and keyboards can control the laptop from the pulpit and put the projector to get the laptop closer to get a better image. For PowerPoint presentations that should be enough.