I can't change the orientation, it is part of a (portrait) document. Calibri is used, smallest size is 8.

You can change the orientation of a single section (page) in Word. Insert a Section break (next page) and change the orientation to Landscape. Then insert another Section break (next page after your table and change back to Portrait.

Or, select your table and change the orientation to Landscape which should automatically insert the section breaks.

Sections / Headers and Footers in Microsoft Word 2007-2010