Maybe this could be a solution for my forum too?
So, as you said, I have contacted my server host.
Asked him if he know what this cron.php is, he said that he didn't know what this is, so we guessed, that there may be an option somewhere in the Administration Control Panel about this cron jobs.. After 5 minutes of search, I have found it:
General > Server Settings >
Run periodic tasks from system cron:
When off, phpBB will arrange for periodic tasks to be run automatically. When on, phpBB will not schedule any periodic tasks by itself; a system administrator must arrange for bin/phpbbcli.php cron:run to be run by the system cron facility at regular intervals (e.g. every 5 minutes).
Turn this to No. The text says that this time, the system admin must arrange the cron to run periodically for example after every 5 minutes.. So My host has changed it to run in every hour. This made all of my periodic Update statements (- all the 80000, these statements ran for 2 minutes), which seems completely pointless to run in every one hour. So, this made my forum to be slow in every hour for 2 minutes. This way, my forum worked correctly. even thoug this background job ran once in every hour. So I though, why not run it once a day, when everyone is asleep at night.
This is my solution.
Should I consult the host about this?