I did this update manually by myself.
1. First i took a look into the table core_view_update... Result --> nearly 195.000 unprocessed entries.
2. Then i export the table entries into a csv file.
3. truncate the table core_view_update
4. group the entries in my csv file
5. import the grouped entries into my forums_topics table
Result
Now i'll check the next days my tasks / cron jobs. At this moment it looked normally
MythonPonty's post in After Update to 4.7.3 - my views doesn't count up was marked as the answer