owncloud. How to allocate user rights?

Question

System administration

Hello. Such situation. There are ordinary users (our customers) who upload certain files to our ftp server to their directories. There is also a certain user with elevated rights, who, when connected to ftp, sees all user folders at the root and can download any file of any user for further work, he is forbidden to delete them. There is an admin who can do whatever he wants. We have implemented all this on proftpd, and there are no problems.
Yes, of course, I know the phrase "WORKING - DO NOT TOUCH!", but there was an idea somehow for the convenience of customers and myself to make a certain service with a web interface. So that customers come to our site in a special subdomain and throw in what they need, and we would pick it up. Closed ftp would be a plus.
I looked at different platforms, the choice fell on OwnCloud: a nice and, most importantly, simple interface. Plus https (encryption after all, security) I
installed and launched everything. The problem is how to make it exactly the way it is now. That is, the customer uploads files to his root folder, and on our side, the user sees all the customers' folders in his root and can take any files for himself, but he cannot delete anything. Plus, he will have the right to create new users, but not delete them. And the admin, as usual, can do everything.
I've read the manuals and nothing is described there. I’ve been studying Google for three days, but there is also deaf on this topic.
Maybe try another service? I have already painted such a beautiful picture for my boss, how cool everything will work.
UPD: I tried to make folders for users and share them for a group that includes a more experienced user (the one who sees all customers) and removed the rights to delete, but he can still delete this share from his directory.

Answer 1

How many customers?
If there are not so many of them, then the plan is this:
1. Create an SMB file share, with a folder structure.
2. Organize access for the user and the administrator at the level of the shares - by delimiting the rights to it and let them go to it directly via SMB through the explorer.
3. We create external storages in ownCloud, each customer has its own, we allow the storage to be seen only by a certain user, and we point the path to a specific folder in the file ball (not to the root)
Such a ball will appear in the user interface as a regular folder, with different ) rights, the customer will be able to fully use it.
It all comes down to quantity. If tens - the decision of the norms, if hundreds - not the norms.

Answer 2

Better yourself. If you look for a similar slider, you will find something similar to it and you will sit all day figuring out how to set it up for yourself and in the end you will castrate it or do nothing (judging by myself)