Thank you all for your useful answers
I had the fear that this won't be easy... I'll now try to get my IT-Department to set it up for me on a virtual server where i run a local moodle page which is the copy of ours and then I'll backup the course and try to get it back on the real one or I'll save the important data and try to recreate it..
From now on I put every course on automatic backup, no matter how much space it takes..
Thanks again!