After I found the exact sector beginning and end of the NTFS partition with MiniTool Power Wizard, I kept looking for ext4 superblocks after that partition with the following command:

$ sudoddif=/dev/sdb of=/dev/stdout bs=512skip=1304581count=1000|hexdump-C|grep-e'......30  .. .. .. .. .. .. .. ..  53 ef .. .. .. .. .. ..'
if has to be the drive where you want to search, skip is the current offset from where you start looking. hexdump outputs the bytes. With grep I looked for rows that ended on i30, where i has to be even. "53 ef" is the ext4 superblock.

After that I could use mount to try to mount that point:

$ sudo mount -o offset=$((1304581 * 512)) /dev/sda /mnt/whereever
I used the offset and bytesize and mount it whereever I want.

Finally I found the / partition and thus the /home partition. As my /home partition was encrypted I used

$ sudo ecryptfs-recover-private
to recover my data. The only thing you need for that is the wrapped-passphrase and your passphrase you used to encrypt the home folder.

ecryptfs-recover-private will mount the drive as read-only in /tmp/.

As I only want to recover my data and now install a fresh system I will mark this as solved.

Thanks again to YesWeCan for his help!