On your own server I would recommend to create a valid crontab entry instead of using web cron. Please study the administrator guide which shows you in detail how the cron.php script need to be executed and a crontab entry need tp look like.
The Instance is in a shared hosting environment, I cannot create cronjobs.
I can run php /nextcloud-install-dir/cron.php
This seems to work.
But none of the other methods do work.