May i know if the user had deleted files and it will goes to the deleted files garbage and how long will it takes to remain at there? 30 days or else?
https://doc.owncloud.org/server/latest/admin_manual/configuration/files/trashbin_options.html
Can all be configured 
thanks for the info, if i didn't do anything, it will permanently store at there unless i do manually or auto right
If you have unlimited quota, yes. Otherwise it depends on storage usage.
how to configure it? with command? i can't get it, please advice
Did you follow the documentation above? Where exactly is it unclear what needs to be done.