We run a Cloudron instance which does use Nextcloud quite extensively. That said, there is about 150GB of data stored on it. The disk size of the instance is 250GB.
That said, we run into an "out of disk space" issue all few months, since Nextcloud stores trashed files for 180 days by default.
Where can I change the 180 days to 60 days for example?
The setting would be
trashbin_retention_obligationas documented in https://docs.nextcloud.com/server/12/admin_manual/configuration_server/config_sample_php_parameters.html#deleted-items-trash-bin
This is unset in the Cloudron app package, so it defaults to auto, which in your case probably does not actually delete files until 100% of the disk space is used. You should be able to adjust the config.php accordingly inside the app, the values should be preserved across restarts.