With those tools you only need to add the hostname of your server, the user, password and port (usually 22).
If that doesn’t work, edit manually /etc/ssh/sshd_config and remove user Saad:
Before:
Match User sftp_dummy99,Irfan_thefrozenfarms,Irfan_thefrozenfarmsWeb,Saad
After:
Match User sftp_dummy99,Irfan_thefrozenfarms,Irfan_thefrozenfarmsWeb
Save the file and restart ssh: systemctl restart ssh
Now try again using File Manager or/and an external client.