First of all, thank you very much for your help. I didn't expect to get so much useful information in such a short time.
I have already contacted Graphtec Japan, USA, Germany and the Netherlands without receiving any help. As I said, the cutter is in like new condition and has no problems so far. My only problem is controlling the cutting plotter via software.
@darcshadow & @Dakotagrafx
Thank you for the information. Since my machine no longer receives support from Graphtec and no suitable software, firmware and drivers are offered for it, I wanted to install the firmware for a similar model. After your posts I will now keep my hands off it.
That was really useful! Unfortunately, I am not familiar with cutting plotters, as this is my first. I have now looked at both of the proposed software and will probably get myself a license for “VinylMaster Cut”.
I will hopefully report on it soon when I have made my first cuts.