Moving Postgres 10 data dir on Ubuntu 18
Please check the socket file is in the /tmp. If it is there then create a link to /var/run.

OR,
I prefer this method to move the data directory on Ubuntu.

I hope you have the backup copy of the old directory which is in /var/lib/postgresql/10/main.

service postgresql stop
rm -rf /media/chris/Datenspeicher/*
chown -R postgres:postgres /media/chris/Datenspeicher/
chmod 700 /media/chris/Datenspeicher
/usr/lib/postgresql/10/bin/initdb -D /media/chris/Datenspeicher
rm -rf /media/chris/Datenspeicher/*
sudo rsync -av /var/lib/postgresql/10/main/* /media/chris/Datenspeicher
in postgresql.conf file,  data_directory = '/media/chris/Datenspeicher'
service postgresql start