Hi Harrie and Damir,
Normally the slow performance is fixed by resetting the preferences as suggested above. If it has not helped trying the key combinations, please manually delete the preferences folders or rename them (if you need to keep the old ones, just in case). For that please see : Set preferences in Adobe InDesign and http://www.tech4pub.com/2012/10/10/indesign-tip-reset-preferences-to-improve-performance
If it still does not fix the issue, please share your system details like OS, Processor, RAM, Graphic Card, etc and InDesign Version for further assistance.
Resets did not help. InDesign is CS6, OSX is 10.11.6, computer is MacBook Pro (Retina, Mid 2012), Processor 2,6 GHz Intel Core i7, Memory 16 GB 1600 MHz DDR3, Graphics Intel HD Graphics 4000 1536 MB.