Connect via Finder with the server, register permissions?

I try to access my FTP server via the Finder. I can open the server and access the files. But when I try to change a .css file or something and save I then get an error stating that I do not have permission.

I tried this but it did not work https://support.apple.com/en-us/HT203538. On my server, the permissions are correct.

Someone knows what I'm doing wrong?