Hi Manfred, sorry I do not speak German, but it looks like you are probably asking about running out of memory when exporting a large mesh file?

MoI is a 32-bit program and so it is not able to use all of your 12GB, if it is running out of memory you will need to do the export in some separate pieces rather than all at once. You can export different pieces of your model by selecting some parts and then using File > Export to write out the file, rather than "Save As". Export only writes the selected objects out to the file and not everything like SaveAs.

Also if you have a file with complex surfaces in it and you have a many-core machine, it is possible that the use of multiple cores during the export may be making things worse as far as a high peak memory usage goes. If that's the case see this message for a setting you can use to limit the number of CPU cores being used:
http://moi3d.com/forum/index.php?webtag=MOI&msg=5124.16

- Michael