What are your computer's specs? It may be that it just cannot handle such a humongous model. Honestly, I have never heard of such a huge model size before (in ArchiCAD). I am just wondering what can be in it to make is so huge?
Is the Compress File checkbox checked in the Options subdialog of the Save As Dialog?
Do you have lots of bitmaps or DWG files placed into the file?
As a first step I would try to bring that file size down.
This article gives some tips on how to do that:
http://www.archicadwiki.com/FileSize
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AMD Ryzen9 5900X CPU, 64 GB RAM 3600 MHz, Nvidia GTX 1060 6GB, 500 GB NVMe SSD
2x28" (2560x1440), Windows 10 PRO ENG, Ac20-Ac28