Thanks for your reply to my issue.
Yes I do, there is z-index value. Here are all my css properties for the full-screen:
Thank you for your further help.
Indeed it was the z-index properties. I played around a little bit, and found out that the z-index value of the qlik mouse-over object is determinated something around 1010-1020.
I simply set the z-index value of my fullscreen object lower than 1010 and everything works perfect. Thank you Ann-Louise for the right hint