I found a solution that worked, at least for the last 3 days. First I did everything, that was suggested in other discussions to remove FulltrustNotifier. After getting the pop-up again and again, I went to Taskmanager (right-click on the Windows Icon) and there I found FullTrustNotifier under the Backgroundprocesses. Curious where the process would be located after having follewed the earlier instructions to remove the program, I clicked on File Location. There I found 3 locations of which 2 had a reference to Adobe and FullTrustNotifer. I deleted both. Adobe is still working and no pop-ups anymore.