Thank you for the quick response. I stayed up a few hours longer and finally found my "mistake". At first I had placed the TOC inside a textframe from the master page. I had no reason to assume I had to add a text frame first. This didnt work because i couldnt let the longer TOC flow over into the next page.
I then realized I should perhaps use a text frame. I created one and tried to squeeze the TOC I already had into it, but this somehow (it was late so i might have done something wrong there) didnt work out well because there was still no overflow into the next page after linking the frame i made to one on the next (empty) page.
Finally I did the one right thing ..... I deleted the TOC and started all over ..... made a text frame ...added the TOC ... linked it ...and ..... it worked!!!!
But..... now all my adjusted styles from the TOC were gone.
I thought there would be a possibility to Save my styles from a file but could only find the options to "Save styles as default" or "Import styles".
So i had to either create all the adjusted styles i had made for the TOC again or set them first as default and then create the new TOC. I have choosen this last option, but i am really wondering why there isnt a possibility to save all Styles in a "Style file". That would be a very welcome addition I think (or is it already there but did i miss it?).