I wonder when it happens the first time that the answer to a question arrives before I have sent the question!
You guys are supersonic, thanks!
So,
Eau Rouge is right, I downloaded the full 10.11.4 dmg and after unpacking etc. I got this message that 10.11 is needed to update to 10.11.4 - which I thought means some previous releases like 10.11.1, .2 or .3 ... So I stopped it. This cannot be just a warning message telling me what I am about to do anyway, I mean we don't talk about Windows...
Well then: Should I ignore the hint (I'm not sure whether the system would continue the install anyway, but I can try)
@Grant: I know about the limitations with other programs, I had this on my MacBook, too, and there were workarounds using old flash plugins that did the job for Adobe apps. And all the rest works smoothly. (Except mail which takes forever to load my mails - but this can be due to the amount of emails or the slow data rate.) The reason why I want to update the iMac is that the calendar agent app crashes every couple of secs, and this drives me nuts. Switching it off is no solution if you use external cals, so I thought to solve the problem with a full new installation.
Waiting for your reply - many thanks in advance from Germany