So i tried to add support by editing /etc/ssh/ssh_config
As per joan's comment, there is a difference between ssh_config and sshd_config:
ssh_config provides a default configuration for SSH clients connecting from this machine to another machine's ssh server, aka. sshd; here d is for daemon. Servers of all kinds usually but not necessarily operate in this mode.
sshd_config provides configuration for this machine's ssh server, sshd.
This can get a bit confusing because sometimes (I think this is the case on Raspbian), the init service which starts the ssh daemon (sshd) is just called ssh, which is also the name of the ssh client.
So, if you are trying to ssh into the pi, you are trying to connect to an sshd running there (technically there can be more than one, but this would be unusual). This includes making sftp connections. The default configuration for this server is /etc/ssh/sshd_config.
There are separate man pages, see man sshd_config and man ssh_config. These go into more detail with regard to the possible options in each file.
There's also a likely problem with your list of ciphers; if you look in man sshd_config under Ciphers you'll see a list, but since this is a hardcoded, stock manual page, it's also worth noting that you get an actual list of what's really available on the machine with ssh -Q cipher. E.g., I notice on a recent Raspbian Jessie that list has one additional entry for rijndael-cbc (which I think is probably an alternate implementation of one of the aes-cbc cipher). Anyway...
Ciphers 3des,aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc
^^^^
I think one of these is not available. You might get more information about the error by running sudo tail -n 50 /var/log/syslog after trying to restart the server.
