ftp user permissions for a directly folder Ubuntu 18.04 VSFTPD

I want to create an ftp newuser that will get access to another user (root).

Example of root tree structure:

root
├── Image
├── server
│   ├── reamder.txt
│   └── start-server
│       ├── start.sh
│       └── text.txt
└── Videos

I want to access the root user to the start-server folder when I open the newuser via ftp.

I can see the start-server and change anything in there, but I am not able to go back.

This is information about my system:

I already got ftp users, but I want them to connect to a specific location as I said before.