Data recovery - damaged filesystem

I've recently installed new distribution (ubuntu 16.04, before it was ubuntu 14.04). Before installation I've copied my data on external hdd. When I was trying to copy it back, I was not able to access it. It seems that the file system (ext4) is damaged. I was able to see it with fdisk -l commnad but not to mount it. I've created mounting point in /media named external

I've run sudo mount /dev/sdb1 /media/external

The output is:

 mount: wrong fs type, bad option, bad superblock on /dev/sdb1,
        missing codepage or helper program, or other error

      In some cases useful info is found in syslog - try
      dmesg | tail or so.

I've tried mount -t ext4 /dev/sdb1 /media/external

Output:

mount: special device /dev/sdb1 does not exist
maria@maria-Vostro-3360:/media$ 

I was also trying to boot the computer on live ubuntu 14.04, the system which was installed when I was copying the data on the external disc, but it didn't help.

Gparted shows unknown file system and under the details there is following:

I've run testdisk. I'm not sure if I've done it correctly (for exemple I don't know if I should choose no partitionned or there was one partition on my disc. I've choose the default options, i.e. partitioned, type - Linux. The result of deep search was"

Disk /dev/sdb - 320 GB / 298 GiB - CHS 38913 255 63
     Partition               Start        End    Size in sectors
 D Linux                    0  32 33 38913  70  5  625139712
 D Linux                 1215 170 44 38913  70  5  605612032
 D Linux                 1490 100 19 38913  70  5  601198592
 D Linux                19611 118 28 25015 239 56   86822912

Since it seems the filesystem is damaged I wanted to run fsck. I've run sudo fsck -r /dev/sdb1 and I got this:

fsck from util-linux 2.27.1
e2fsck 1.42.13 (17-May-2015)
ext2fs_open2: Bad magic number in super-block
fsck.ext2: Superblock invalid, trying backup blocks...
Superblock has an invalid journal (inode 8).
Clear<y>? 

Since I don't understand really what I am doing, I typed no, I don't want to mess it up more and loose my data defenitly. The output was:

fsck.ext2: Illegal inode number while checking ext3 journal for /dev/sdb1

/dev/sdb1: ***** FILE SYSTEM WAS MODIFIED *****

/dev/sdb1: ********** WARNING: Filesystem still has errors **********

/dev/sdb1: status 12, rss 3040, real 816.797699, user 0.004000, sys 0.000000

UPDATE: In testdisk I've tried to check the non partitioned media. Than Advanced - filesystem utiles shows primary partition with unknown filesystem. I've tried to change it to ext4 and than entered list. The output was: Can't open filesystem. Filesystem seems damaged.

UPDATE 2: Following @heynnema's advice I've managed to recover something but I still don't know exactly what. All the files and directories are in one directory lost+found with wired names (starting by # and after different numbers). Some of files has name of a file that I had in my computer but the name doesn't match with the content. To open the folder lost+found I have to use sudo and I'm not able to copy it:

root@maria-Vostro-3360:/media/maria/9db3c007-4387-4ea8-a61c-b12fa10049bc/lost+found/#3670019# cp -i /media/maria/9db3c007-4387-4ea8-a61c-b12fa10049bc/lost+found/#4718697/ /home/maria/Desktop/odzysk/1
cp: omitting directory '/media/maria/9db3c007-4387-4ea8-a61c-b12fa10049bc/lost+found/#4718697/'

The .odt file after opening it looks like this: It was loading very long and finally I got the message that it contains some invalid characters. While I was trying to change the encoding, the file closed due to some error.