Are you using your CPanel login as your FTP user? Does your client give you the option to go to the parent directory, often displayed as a folder named '..'? I would use ftp://arlind.tk as your server, but I don't think it matters as long as you use the correct user. If you log in as ftp@arlind.tk or anonymous@arlind.tk, you will be inside the public_ftp folder and cannot see anything outside of it.