I think you have encountered a short-coming in DOSBox. I remember someone running a Chinese application in DOSBox who had a similar problem. 2/3 or so of the Chinese signs where missing. If I remember correctly, the conclusion was that the application - and yours too - probably tries to upload the characters into parts of the video-memory. For a hardware VGA/graphics card it will work, but it appears like that functionality is not (yet) a part of DOSBox.

Edit: Yep - here is the thread.
NANPA2: VDMSOUND=Text/Yes, Sound/No. DOSBOX=Text/No, Sound/Yes

Thank you for your answer.
I do not think, that the program is using - in some way - special fonts that cannot be uploaded. As I said, the screen where the right side is missing is a chart. I suppose the app draws it on its own.

I tired several changes with fullresolution, hwscale and scaler which did not change anything.

Did you try changing the machine type? The default is 'vga'. Try 'hercules', 'tandy' or 'cga' (if it is still there).

I tired all of them. The only thing that changes is sometimes the color of the background but the porblem stays.