Deny upload on root directory

Hi guys,

Maybe one of you can help, at the moment I have 3 companies / groups with 3 separate data directories (basically 3 hard drives via Azure) the main data directory which Nextcloud uses is number 1 and the other 2 is connected via external storages. Basically I have other people logging in and I want them accessing just their files by going to their external storage however I need to don’t want them to upload any files / folders out of the external storage (basically their personal directory) and only on their external storage. May someone help, I can of course change the permissions on number 1 directory for their home folder to deny access but usually that makes loads of errors appear?