Multi users to login webui?

Is it possible to set my my server so a friend can run his own server, but not be able to have access to my servers and files?

Yes
In a MineOS ssh shell:
sudo adduser {username}

That user will have access to MineOS, but only to servers that user has created

I assume you mean in WebUI their user will display only their servers?

I tried in WInSCP got eror and also in putty as root I get this
root@mineos-tkldev /home/mc# sudo adduser Golvore
bash: sudo: command not found

If you are logged in as root, you can omit the “sudo” part of the command. You shoudl really never use the root user unless you are updating or upgrading.

as mc
mc@mineos-tkldev ~$ sudo adduser Golvore
-bash: sudo: command not found

All commands I do run if they start with sudo I need to remove it

I was under the impression a different user couldn’t see my server files, if I log into my server via WinSCP I can see and edit all files on my server.

I would try installing sudo using su
Then add the account, you should also be able to add the sudo permission at the same time.
I would also recommend adding mc to sudo.

I was able to create the user via root, but I think they inherited root rights since they could view all the files on the server via ftp. If I use su it thinks I want to switch users

mc@mineos-tkldev ~$ su adduser golvore
No passwd entry for user ‘adduser’

In short, the group permissions may allow to see the files, but to read, write or execute, may be prevented. if you run the command ls -l it will list the files and shows the permissions for the user/group/global, read as -rwxrwxrwx (the dash denotes that item is a directory.)

You should also be able to see who is the owner (something.like root:root)