Permanently remove deleted and unused files

I really do not like plugins which I’ve deleted still to keep some trackers, files or customization. I’ve had situations where a website starts giving errors because of that. It’s strange because it looks like they don’t keep any files in the file manager, in the php you can find something. Currently, Sucuri set automatically executions for something I do not use. And in the php I see there is something else that I’ve just tried, and I did not like it.

So how could I add some cron jobs or something for that problem?

The page I need help with: [log in to see the link]